CYT28 serpentine receptor disruptions, compositions and methods relating thereto

ABSTRACT

The present invention relates to compositions and methods relating to the characterization and function of CYT28. Specifically, the present invention provides transgenic animals comprising disruptions in a CYT28 gene and methods of treating diseases conditions, such as pain. The present invention further relates to agents that modulate CYT28 and methods of screening for agents that modulate CYT28 for the treatment of diseases and conditions such as pain.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/179,410 filed Jun. 24, 2002, which claims benefit of U.S. ProvisionalApplication No. 60/301,009, filed Jun. 26, 2001, and U.S. ProvisionalApplication No. 60/366,611, filed Mar. 22, 2002, the entire contents ofeach of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to compositions, including transgenicanimals and methods relating to the characterization of gene function.

BACKGROUND OF THE INVENTION

Many medically significant biological processes are mediated by proteinsparticipating in signal transduction pathways that involve G-proteinsand/or second messengers such as cAMP. The membrane protein genesuperfamily of G-protein coupled receptors (GPCRs) include a wide rangeof biologically active receptors, such as hormone, viral, growth factorand neuroreceptors. GPCRs have been characterized as having sevenputative transmembrane domains (designated TM1, TM2, TM3, TM4, TM5, TM6,and TM7), which are believed to represent transmembrane α-helicesconnected by extracellular or cytoplasmic loops. Most G-protein coupledreceptors have single conserved cysteine residues in each of the firsttwo extracellular loops which form disulfide bonds that are believed tostabilize functional protein structure. G-protein coupled receptors canbe intracellularly coupled by heterotrimeric G-proteins to variousintracellular enzymes, ion channels and transporters. DifferentG-protein α-subunits preferentially stimulate particular effectors tomodulate various biological functions in a cell.

Seven-transmembrane domain GPCRs (aka serpentine receptors) are involvedin signaling in response to a diverse array of agonists. In fact, thebody uses seven membrane-spanning serpentine receptors for an astoundingvariety of biological signaling functions. Serpentine receptors do notdepend upon receptor dimerization in order to transduce signals acrossthe plasma membrane. Instead, single receptor molecules will changetheir three-dimensional steric configuration in response to ligandbinding. This steric shift affects the configuration of the cytoplasmicdomains of the receptor (i.e., the loops of receptor protein thatprotrude into the cytoplasm).

One member of the serpentine receptor subfamily is CYT28, the complete3021 bp cds for which has been deposited in GenBank (Accession No.:AF166382; GI No.: 6006810).

Given the importance of GPCRs in biological and disease processes, aclear need exists for further in vivo characterization, which may aid inthe identification and discovery of therapeutics and treatments usefulin preventing, ameliorating or correcting dysfunctions or diseases.

SUMMARY OF THE INVENTION

The present invention generally relates to compositions, includingtransgenic animals and methods relating to the characterization,function and uses of the CYT28 serpentine receptor.

The present invention provides transgenic cells comprising a disruptionin a CYT28 gene. The transgenic cells of the present invention arecomprised of any cells capable of undergoing homologous recombination.Preferably, the cells of the present invention are stem cells and morepreferably, embryonic stem (ES) cells, and most preferably, murine EScells. According to one embodiment, the transgenic cells are produced byintroducing a targeting construct into a stem cell to produce ahomologous recombinant, resulting in a mutation of the CYT28 gene. Inanother embodiment, the transgenic cells are derived from the transgenicanimals described below. The cells derived from the transgenic animalsincludes cells that are isolated or present in a tissue or organ, andany cell lines or any progeny thereof.

The present invention also provides a targeting construct and methods ofproducing the targeting construct that when introduced into stem cellsproduces a homologous recombinant. In one embodiment, the targetingconstruct of the present invention comprises first and secondpolynucleotide sequences that are homologous to the CYT28 gene. Thetargeting construct may also comprise a polynucleotide sequence thatencodes a selectable marker that is preferably positioned between thetwo different homologous polynucleotide sequences in the construct. Thetargeting construct may also comprise other regulatory elements that canenhance homologous recombination.

The present invention further provides non-human transgenic animals andmethods of producing such non-human transgenic animals comprising adisruption in a CYT28 gene. The transgenic animals of the presentinvention include transgenic animals that are heterozygous andhomozygous for a null mutation in the CYT28 gene. In one aspect, thetransgenic animals of the present invention are defective in thefunction of the CYT28 gene. In another aspect, the transgenic animals ofthe present invention comprise a phenotype associated with having amutation in a CYT28 gene. Preferably, the transgenic animals are rodentsand, most preferably, are mice.

In a preferred embodiment, the present invention provides a transgenicmouse comprising a disruption in a CYT28 gene, wherein there is nonative expression of the endogenous CYT28 gene.

In one aspect of the present invention, a transgenic mouse having adisruption in the CYT28 gene exhibits a phenotype consistent with one ormore symptoms of a disease associated with CYT28. Alternatively, atransgenic mouse having a disruption in the CYT28 gene may exhibit aphenotype associated with a function of CYT28.

In one aspect, a transgenic mouse having a homozygous disruption in theCYT28 gene exhibits decreased response latency to a thermal stimulus.More specifically, the decreased response latency may be characterizedin a hot plate test. In accordance with this aspect, the transgenicmouse having a disruption in the CYT28 gene exhibits a phenotypecomprising pain sensitivity or pain hypersensitivity.

In another aspect of the present invention, transgenic mice having ahomozygous disruption in the CYT28 gene exhibit an increased velocity ofmovement. More specifically, the increased velocity is detected in anopen field test. In accordance with this aspect, the transgenic miceexhibit decreased anxiety, increased activity (hyperactivity), orincreased mobility.

In another aspect of the present invention, transgenic mice having ahomozygous disruption in the CYT28 gene exhibit a brain abnormality. Inparticular, the transgenic mice exhibit a brain abnormality comprisingcortical malformation, which may be characterized by dysplasia of thelayers in the cerebellar cortex. Homozygous mutant mice further compriseirregularly formed granular cell and Purkinje cell layers.

In another aspect of the present invention, transgenic mice having adisruption in the CYT28 gene exhibit a lipoma, which in one aspect,correlates with a mesenteric mass. The transgenic mice having ahomozygous disruption in the CYT28 gene may also exhibit Leydig celladenoma of the testis.

The transgenic mice of the present invention may be used as an in vivomodel to study various disease states or conditions in which CYT28 maybe implicated or may be involved, such as pain. The transgenic mice ofthe present invention may also be used to evaluate various treatments orto identify agents for the treatment of disease states or conditions inwhich CYT28 may be implicated or may be involved, such as pain. Inaddition, cells comprising a disruption in the CYT28 gene, includingcells derived from the transgenic animals of the present invention, mayalso be used in the study of or to evaluate or identify treatments fordisease states or conditions in which CYT28 may be implicated, such aspain.

The present invention also provides methods of identifying agentscapable of affecting a phenotype of a transgenic animal. For example, aputative agent is administered to the transgenic animal and a responseof the transgenic animal to the putative agent is measured and comparedto the response of a “normal” or wild-type mouse, or alternativelycompared to a transgenic animal control (without agent administration).The invention further provides agents identified according to suchmethods. The present invention also provides methods of identifyingagents useful as therapeutic agents for treating conditions associatedwith a disruption or other mutation (including naturally occurringmutations) of the CYT28 gene.

One aspect of the present invention relates to a method of identifying apotential therapeutic agent for the treatment of a disease associatedwith the CYT28 gene, in which the method includes the steps ofadministering the potential therapeutic agent to a transgenic mousehaving a disruption in a CYT28 gene and determining whether thepotential therapeutic agent modulates the disease associated with theCYT28 gene, wherein the modulation of the disease identifies a potentialtherapeutic agent for the treatment of that disease.

In accordance with this aspect, the present invention provides a methodof identifying a potential therapeutic agent for the treatment of painwhich comprises administering the potential therapeutic agent to atransgenic mouse having a disruption in a CYT28 gene and determiningwhether the potential therapeutic agent modulates pain, wherein themodulation of pain identifies a potential agent for the treatment ofpain hypersensitivity.

A further aspect of the present invention provides a method ofidentifying a potential therapeutic agent for the treatment of a diseaseassociated with the CYT28 gene, in which the method includes the stepsof contacting the potential therapeutic agent with CYT28 gene productand determining whether the potential therapeutic agent modulates thatproduct, wherein modulation of the gene product identifies a potentialtherapeutic agent for the treatment of the disease associated with theCYT28 gene.

In accordance with this aspect, the present invention further provides amethod of identifying a potential therapeutic agent for the treatment ofpain, and more specifically, pain hypersensitivity comprising contactingthe potential therapeutic agent with the CYT28 and determining whetherthe potential therapeutic agent modulates the CYT28, wherein saidmodulation identifies a potential therapeutic agent for the treatment ofpain, for example, pain hypersensitivity.

The present invention further provides a method of identifying agentshaving an effect on CYT28 expression or function. The method includesadministering an effective amount of the agent to a transgenic animal,preferably a mouse. The method includes measuring a response of thetransgenic animal, for example, to the agent, and comparing the responseof the transgenic animal to a control animal, which may be, for example,a wild-type animal or alternatively, a transgenic animal control.Compounds that may have an effect on CYT28 expression or function mayalso be screened against cells in cell-based assays, for example, toidentify such compounds.

The invention also provides cell lines comprising nucleic acid sequencesof a CYT28 gene. Such cell lines may be capable of expressing suchsequences by virtue of operable linkage to a promoter functional in thecell line. Preferably, expression of the CYT28 gene sequence is underthe control of an inducible promoter. Also provided are methods ofidentifying agents that interact with the CYT28 gene, comprising thesteps of contacting the CYT28 gene with an agent and detecting anagent/CYT28 gene complex. Such complexes can be detected by, forexample, measuring expression of an operably linked detectable marker.

The invention further provides methods of treating diseases orconditions associated with a disruption in a CYT28 gene, and moreparticularly, to a disruption or other alteration in the expression orfunction of the CYT28 gene. In a preferred embodiment, methods of thepresent invention involve treating diseases or conditions associatedwith a disruption or other alteration in the CYT28 gene's expression orfunction, including administering to a subject in need, a therapeuticagent that affects CYT28 expression or function. In accordance with thisembodiment, the method comprises administration of a therapeuticallyeffective amount of a natural, synthetic, semi-synthetic, or recombinantCYT28 gene, CYT28 gene products or fragments thereof as well as natural,synthetic, semi-synthetic or recombinant analogs.

In one aspect of the present invention, a therapeutic agent for treatinga disease associated with the CYT28 gene modulates the CYT28 geneproduct. Another aspect of the present invention relates to atherapeutic agent for treating a disease associated with the CYT28 gene,in which the agent is an agonist or antagonist of the CYT28 geneproduct.

In a further aspect of the present invention, a therapeutic agent fortreating pain is provided that modulates the CYT28. In accordance withthis aspect, the present invention provides a therapeutic agent fortreating pain, where in the agent is an agonist of CYT28.

The present invention also provides compositions comprising or derivedfrom ligands or other molecules or compounds that bind to or interactwith CYT28, including agonists or antagonists of CYT28. Such agonists orantagonists of CYT28 include antibodies and antibody mimetics, as wellas other molecules that can readily be identified by routine assays andexperiments well known in the art.

The present invention further provides methods of treating diseases orconditions associated with disrupted targeted gene expression orfunction, wherein the methods comprise detecting and replacing throughgene therapy mutated or otherwise defective or abnormal CYT28 genes.

Definitions

The term “gene” refers to (a) a gene containing at least one of the DNAsequences disclosed herein; (b) any DNA sequence that encodes the aminoacid sequence encoded by the DNA sequences disclosed herein and/or; (c)any DNA sequence that hybridizes to the complement of the codingsequences disclosed herein. Preferably, the term includes coding as wellas noncoding regions, and preferably includes all sequences necessaryfor normal gene expression.

The terms “polynucleotide” and “nucleic acid molecule” are usedinterchangeably to refer to polymeric forms of nucleotides of anylength. The polynucleotides may contain deoxyribonucleotides,ribonucleotides and/or their analogs. Nucleotides may have anythree-dimensional structure, and may perform any function, known orunknown. The term “polynucleotide” includes single-, double-stranded andtriple helical molecules. “Oligonucleotide” refers to polynucleotides ofbetween 5 and about 100 nucleotides of single- or double-stranded DNA.Oligonucleotides are also known as oligomers or oligos and may beisolated from genes, or chemically synthesized by methods known in theart. A “primer” refers to an oligonucleotide, usually single-stranded,that provides a 3′-hydroxyl end for the initiation of enzyme-mediatednucleic acid synthesis. The following are non-limiting embodiments ofpolynucleotides: a gene or gene fragment, exons, introns, mRNA, tRNA,rRNA, ribozymes, cDNA, recombinant polynucleotides, branchedpolynucleotides, plasmids, vectors, isolated DNA of any sequence,isolated RNA of any sequence, nucleic acid probes and primers. A nucleicacid molecule may also comprise modified nucleic acid molecules, such asmethylated nucleic acid molecules and nucleic acid molecule analogs.Analogs of purines and pyrimidines are known in the art, and include,but are not limited to, aziridinycytosine, 4-acetylcytosine,5-fluorouracil, 5-bromouracil, 5-carboxymethylaminomethyl-2-thiouracil,5-carboxymethyl-aminomethyluracil, inosine, N6-isopentenyladenine,1-methyladenine, 1-methylpseudouracil, 1-methylguanine, 1-methylinosine,2,2-dimethylguanine, 2-methyladenine, 2-methylguanine, 3-methylcytosine,5-methylcytosine, pseudouracil, 5-pentylnyluracil and 2,6-diaminopurine.The use of uracil as a substitute for thymine in a deoxyribonucleic acidis also considered an analogous form of pyrimidine.

A “fragment” of a polynucleotide is a polynucleotide comprised of atleast 9 contiguous nucleotides, preferably at least 15 contiguousnucleotides and more preferably at least 45 nucleotides, of coding ornon-coding sequences.

The term “gene targeting” refers to a type of homologous recombinationthat occurs when a fragment of genomic DNA is introduced into amammalian cell and that fragment locates and recombines with endogenoushomologous sequences.

The term “homologous recombination” refers to the exchange of DNAfragments between two DNA molecules or chromatids at the site ofhomologous nucleotide sequences.

The term “homologous” as used herein denotes a characteristic of a DNAsequence having at least about 70 percent sequence identity as comparedto a reference sequence, typically at least about 85 percent sequenceidentity, preferably at least about 95 percent sequence identity, andmore preferably about 98 percent sequence identity, and most preferablyabout 100 percent sequence identity as compared to a reference sequence.Homology can be determined using, for example, a “BLASTN” algorithm. Itis understood that homologous sequences can accommodate insertions,deletions and substitutions in the nucleotide sequence. Thus, linearsequences of nucleotides can be essentially identical even if some ofthe nucleotide residues do not precisely correspond or align. Thereference sequence may be a subset of a larger sequence, such as aportion of a gene or flanking sequence, or a repetitive portion of achromosome.

The term “target gene” (alternatively referred to as “target genesequence” or “target DNA sequence” or “target sequence”) refers to anynucleic acid molecule, polynucleotide, or gene to be modified byhomologous recombination. The target sequence includes an intact gene,an exon or intron, a regulatory sequence or any region between genes.The target gene may comprise a portion of a particular gene or geneticlocus in the individual's genomic DNA. As provided herein, the targetgene of the present invention is a CYT28 gene, or a homolog or orthologthereof.

A “CYT28” refers to any one of the following: (1) the polynucleotidesequence shown in FIG. 1 (SEQ ID NO:1) or identified in GenBank asAccession No.: AF166382; GI No.: 6006810; (2) the CYT28 protein as shownin FIG. 2 (SEQ ID NO:2) or identified in GenBank Accession No.:AAF00617; GI No.: 6006811; or (3) any homologues of the above identifiedsequences.

The term “CYT28 molecule” refers to CYT28 as defined above or variants,derivatives, active fragments or mutants of CYT28.

As used herein, a “variant” of CYT28 is defined as an amino acidsequence that is different by one or more amino acid substitutions. Thevariant may have “conservative” changes, wherein a substituted aminoacid has similar structural or chemical properties, e.g., replacement ofa leucine with isoleucine. More rarely, a variant may have“nonconservative” changes, e.g., replacement of a glycine with atryptophan. Similar minor variations may also include amino aciddeletions or insertions, or both. Guidance in determining which and howmany amino acid residues may be substituted, inserted or deleted withoutabolishing biological or immunological activity may be found usingcomputer programs well known in the art, for example, DNAStar software.

The term “active fragment” refers to a fragment of a CYT28 that isbiologically or immunologically active. The term “biologically active”refers to a CYT28 having structural, regulatory or biochemical functionsof the naturally occurring CYT28. Likewise, “immunologically active”defines the capability of the natural, recombinant or synthetic CYT28,or any oligopeptide thereof, to induce a specific immune response inappropriate animals or cells and to bind with specific antibodies.

The term “derivative”, as used herein, refers to the chemicalmodification of a nucleic acid sequence encoding a CYT28 or the encodedCYT28 protein. An example of such modifications would be replacement ofhydrogen by an alkyl, acyl, or amino group. A nucleic acid derivativewould encode a polypeptide which retains essential biologicalcharacteristics of a natural CYT28.

“Disruption” of a CYT28 gene occurs when a fragment of genomic DNAlocates and recombines with an endogenous homologous sequence. Thesesequence disruptions or modifications may include insertions, missense,frameshift, deletion, or substitutions, or replacements of DNA sequence,or any combination thereof. Insertions include the insertion of entiregenes, which may be of animal, plant, fungal, insect, prokaryotic, orviral origin. Disruption, for example, can alter the normal gene productby inhibiting its production partially or completely or by enhancing thenormal gene product's activity. In a preferred embodiment, thedisruption is a null disruption, wherein there is no significantexpression of the CYT28 gene.

The term “native expression” refers to the expression of the full-lengthpolypeptide encoded by the CYT28 gene, at expression levels present inthe wild-type mouse. Thus, a disruption in which there is “no nativeexpression” of the endogenous CYT28 gene refers to a partial or completereduction of the expression of at least a portion of a polypeptideencoded by an endogenous CYT28 gene of a single cell, selected cells, orall of the cells of a mammal. The term “knockout” is a synonym forfunctional inactivation of the gene.

The term “construct” or “targeting construct” refers to an artificiallyassembled DNA segment to be transferred into a target tissue, cell lineor animal. Typically, the targeting construct will include a gene or anucleic acid sequence of particular interest, a marker gene andappropriate control sequences. As provided herein, the targetingconstruct of the present invention comprises a CYT28 targetingconstruct. A “CYT28 targeting construct” includes a DNA sequencehomologous to at least one portion of a CYT28 gene and is capable ofproducing a disruption in a CYT28 gene in a host cell.

The term “transgenic cell” refers to a cell containing within its genomea CYT28 gene that has been disrupted, modified, altered, or replacedcompletely or partially by the method of gene targeting.

The term “transgenic animal” refers to an animal that contains withinits genome a specific gene that has been disrupted or otherwise modifiedor mutated by the method of gene targeting. “Transgenic animal” includesboth the heterozygous animal (i.e., one defective allele and onewild-type allele) and the homozygous animal (i.e., two defectivealleles).

As used herein, the terms “selectable marker” and “positive selectionmarker” refer to a gene encoding a product that enables only the cellsthat carry the gene to survive and/or grow under certain conditions. Forexample, plant and animal cells that express the introduced neomycinresistance (Neo^(r)) gene are resistant to the compound G418. Cells thatdo not carry the Neo^(r) gene marker are killed by G418. Other positiveselection markers are known to, or are within the purview of, those ofordinary skill in the art.

A “host cell” includes an individual cell or cell culture that can be orhas been a recipient for vector(s) or for incorporation of nucleic acidmolecules and/or proteins. Host cells include progeny of a single hostcell, and the progeny may not necessarily be completely identical (inmorphology or in total DNA complement) to the original parent due tonatural, accidental, or deliberate mutation. A host cell includes cellstransfected with the constructs of the present invention.

The term “modulates” or “modulation” as used herein refers to thedecrease, inhibition, reduction, amelioration, increase or enhancementof CYT28 function, expression, activity, or alternatively a phenotypeassociated with a disruption in a CYT28 gene. The term “ameliorates” or“amelioration” as used herein refers to a decrease, reduction orelimination of a condition, disease, disorder, or phenotype, includingan abnormality or symptom associated with a disruption in a CYT28 gene.

The term “abnormality” refers to any disease, disorder, condition, orphenotype in which a function of a CYT28 gene is implicated, includingpathological conditions and behavioral observations.

The term “pain” refers to all types of pain, including somatic pain,e.g., visceral pain or cutaneous pain, or pain caused by a burn, abruise, an abrasion, a laceration, a broken bone, a torn ligament, atorn tendon, a torn muscle, a viral infection, a bacterial infection, aprotozoal infection, a fungal infection, contact dermatitis,inflammation, or cancer; and neuropathic pain, e.g. caused by injury tothe central or peripheral nervous system due to cancer, HIV infection,tissue trauma, infection, autoimmune disease, diabetes, arthritis,diabetic neuropathy, trigeminal neuralgia or drug administration.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the polynucleotide sequence for a mouse CYT28 gene (SEQ IDNO:1).

FIG. 2 shows the amino acid sequence for a mouse CYT28 protein (SEQ IDNO:2).

FIGS. 3-4 show the location and extent of the disrupted portion of theCYT28 gene, as well as the nucleotide sequences flanking the Neo^(r)insert in the targeting construct. FIG. 4 shows the sequences identifiedas SEQ ID NO:3 and SEQ ID NO:4, which were used as the 5′- and3′-targeting arms (including the homologous sequences) in the CYT28targeting construct, respectively.

FIG. 5 shows a graph comparing the response latencies (time in secondsto withdraw hindpaw) of homozygous, heterozygous, and wild-type mice toa heat stimulus in the hot plate test.

DETAILED DESCRIPTION OF THE INVENTION

The invention is based, in part, on the evaluation of the expression androle of genes and gene expression products, primarily those associatedwith a CYT28 gene. Among other uses or applications, the inventionpermits the definition of disease pathways and the identification ofdiagnostically and therapeutically useful targets. For example, genesthat are mutated or down-regulated under disease conditions may beinvolved in causing or exacerbating the disease condition. Treatmentsdirected at up-regulating the activity of such genes or treatments thatinvolve alternate pathways, may ameliorate the disease condition.

Generation of Targeting Construct

The targeting construct of the present invention may be produced usingstandard methods known in the art. (see, e.g., Sambrook, et al., 1989,Molecular Cloning: A Laboratory Manual, Second Edition, Cold SpringHarbor Laboratory Press, Cold Spring Harbor, N.Y.; E. N. Glover (eds.),1985, DNA Cloning: A Practical Approach, Volumes I and II; M. J. Gait(ed.), 1984, Oligonucleotide Synthesis; B. D. Hames & S. J. Higgins(eds.), 1985, Nucleic Acid Hybridization; B. D. Hames & S. J. Higgins(eds.), 1984, Transcription and Translation; R. I. Freshney (ed.), 1986,Animal Cell Culture; Immobilized Cells and Enzymes, IRL Press, 1986; B.Perbal, 1984, A Practical Guide To Molecular Cloning; F. M. Ausubel etal., 1994, Current Protocols in Molecular Biology, John Wiley & Sons,Inc.). For example, the targeting construct may be prepared inaccordance with conventional ways, where sequences may be synthesized,isolated from natural sources, manipulated, cloned, ligated, subjectedto in vitro mutagenesis, primer repair, or the like. At various stages,the joined sequences may be cloned, and analyzed by restrictionanalysis, sequencing, or the like.

The targeting DNA can be constructed using techniques well known in theart. For example, the targeting DNA may be produced by chemicalsynthesis of oligonucleotides, nick-translation of a double-stranded DNAtemplate, polymerase chain-reaction amplification of a sequence (orligase chain reaction amplification), purification of prokaryotic ortarget cloning vectors harboring a sequence of interest (e.g., a clonedcDNA or genomic DNA, synthetic DNA or from any of the aforementionedcombination) such as plasmids, phagemids, YACs, cosmids, bacteriophageDNA, other viral DNA or replication intermediates, or purifiedrestriction fragments thereof, as well as other sources of single anddouble-stranded polynucleotides having a desired nucleotide sequence.Moreover, the length of homology may be selected using known methods inthe art. For example, selection may be based on the sequence compositionand complexity of the predetermined endogenous target DNA sequence(s).

The targeting construct of the present invention typically comprises afirst sequence homologous to a portion or region of the CYT28 gene and asecond sequence homologous to a second portion or region of the CYT28gene. The targeting construct may further comprise a positive selectionmarker, which is preferably positioned in between the first and thesecond DNA sequences that are homologous to a portion or region of thetarget DNA sequence. The positive selection marker may be operativelylinked to a promoter and a polyadenylation signal.

Other regulatory sequences known in the art may be incorporated into thetargeting construct to disrupt or control expression of a particulargene in a specific cell type. In addition, the targeting construct mayalso include a sequence coding for a screening marker, for example,green fluorescent protein (GFP), or another modified fluorescentprotein.

Although the size of the homologous sequence is not critical and canrange from as few as about 15-20 base pairs to as many as 100 kb,preferably each fragment is greater than about 1 kb in length, morepreferably between about 1 and about 10 kb, and even more preferablybetween about 1 and about 5 kb. One of skill in the art will recognizethat although larger fragments may increase the number of homologousrecombination events in ES cells, larger fragments will also be moredifficult to clone.

In a preferred embodiment of the present invention, the targetingconstruct is prepared directly from a plasmid genomic library using themethods described in pending U.S. patent application Ser. No.08/971,310, filed Nov. 17, 1997, the disclosure of which is incorporatedherein in its entirety. Generally, a sequence of interest is identifiedand isolated from a plasmid library in a single step using, for example,long-range PCR. Following isolation of this sequence, a secondpolynucleotide that will disrupt the target sequence can be readilyinserted between two regions encoding the sequence of interest. Inaccordance with this aspect, the construct is generated in two steps by(1) amplifying (for example, using long-range PCR) sequences homologousto the target sequence, and (2) inserting another polynucleotide (forexample a selectable marker) into the PCR product so that it is flankedby the homologous sequences. Typically, the vector is a plasmid from aplasmid genomic library. The completed construct is also typically acircular plasmid.

In another embodiment, the targeting construct is designed in accordancewith the regulated positive selection method described in U.S. patentapplication Ser. No. 09/954,483, filed Sep. 17, 2001, the disclosure ofwhich is incorporated herein in its entirety. The targeting construct isdesigned to include a PGK-neo fusion gene having two lacO sites,positioned in the PGK promoter and an NLS-lacI gene comprising a lacrepressor fused to sequences encoding the NLS from the SV40 T antigen.

In another embodiment, the targeting construct may contain more than oneselectable maker gene, including a negative selectable marker, such asthe herpes simplex virus tk (HSV-tk) gene. The negative selectablemarker may be operatively linked to a promoter and a polyadenylationsignal. (see, e.g., U.S. Pat. No. 5,464,764; U.S. Pat. No. 5,487,992;U.S. Pat. No. 5,627,059; and U.S. Pat. No. 5,631,153).

Generation of Cells and Confirmation of Homologous Recombination Events

Once an appropriate targeting construct has been prepared, the targetingconstruct may be introduced into an appropriate host cell using anymethod known in the art. Various techniques may be employed in thepresent invention, including, for example: pronuclear microinjection;retrovirus mediated gene transfer into germ lines; gene targeting inembryonic stem cells; electroporation of embryos; sperm-mediated genetransfer; and calcium phosphate/DNA co-precipitates, microinjection ofDNA into the nucleus, bacterial protoplast fusion with intact cells,transfection, polycations, e.g., polybrene, polyomithine, etc., or thelike (see, e.g., U.S. Pat. No. 4,873,191; Van der Putten, et al., 1985,Proc. Natl. Acad. Sci., USA 82:6148-6152; Thompson, et al., 1989, Cell56:313-321; Lo, 1983, Mol Cell. Biol. 3:1803-1814; Lavitrano, et al.,1989, Cell, 57:717-723). Various techniques for transforming mammaliancells are known in the art. (see, e.g., Gordon, 1989, Intl. Rev. Cytol.,115:171-229; Keown et al., 1989, Methods in Enzymology; Keown et al.,1990, Methods and Enzymology, Vol. 185, pp. 527-537; Mansour et al.,1988, Nature, 336:348-352).

In a preferred aspect of the present invention, the targeting constructis introduced into host cells by electroporation. In this process,electrical impulses of high field strength reversibly permeabilizebiomembranes allowing the introduction of the construct. The porescreated during electroporation permit the uptake of macromolecules suchas DNA. (see, e.g., Potter, H., et al., 1984, Proc. Nat'l. Acad. Sci.U.S.A. 81:7161-7165).

Any cell type capable of homologous recombination may be used in thepractice of the present invention. Examples of such target cells includecells derived from vertebrates including mammals such as humans, bovinespecies, ovine species, murine species, simian species, and ethereucaryotic organisms such as filamentous fungi, and higher multicellularorganisms such as plants.

Preferred cell types include embryonic stem (ES) cells, which aretypically obtained from pre-implantation embryos cultured in vitro.(see, e.g., Evans, M. J., et al., 1981 , Nature 292:154-156; Bradley, M.O., et al., 1984, Nature 309:255-258; Gossler et al., 1986, Proc. Natl.Acad. Sci. USA 83:9065-9069; and Robertson, et al., 1986, Nature322:445-448). The ES cells are cultured and prepared for introduction ofthe targeting construct using methods well known to the skilled artisan.(see, e.g., Robertson, E. J. ed. “Teratocarcinomas and Embryonic StemCells, a Practical Approach”, IRL Press, Washington D.C., 1987; Bradleyet al., 1986, Current Topics in Devel. Biol. 20:357-371; by Hogan etal., in “Manipulating the Mouse Embryo”: A Laboratory Manual, ColdSpring Harbor Laboratory Press, Cold Spring Harbor N.Y., 1986; Thomas etal., 1987, Cell 51:503; Koller et al., 1991, Proc. Natl. Acad. Sci. USA,88:10730; Dorin et al., 1992, Transgenic Res. 1:101; and Veis et al.,1993, Cell 75:229). The ES cells that will be inserted with thetargeting construct are derived from an embryo or blastocyst of the samespecies as the developing embryo into which they are to be introduced.ES cells are typically selected for their ability to integrate into theinner cell mass and contribute to the germ line of an individual whenintroduced into the mammal in an embryo at the blastocyst stage ofdevelopment. Thus, any ES cell line having this capability is suitablefor use in the practice of the present invention.

The present invention may also be used to knock out or otherwise modifyor disrupt genes in other cell types, such as stem cells. By way ofexample, stem cells may be myeloid, lymphoid, or neural progenitor andprecursor cells. These cells comprising a knock out, modification ordisruption of a gene may be particularly useful in the study of CYT28gene function in individual developmental pathways. Stem cells may bederived from any vertebrate species, such as mouse, rat, dog, cat, pig,rabbit, human, non-human primates and the like.

After the targeting construct has been introduced into cells, the cellsin which successful gene targeting has occurred are identified.Insertion of the targeting construct into the targeted gene is typicallydetected by identifying cells for expression of the marker gene. In apreferred embodiment, the cells transformed with the targeting constructof the present invention are subjected to treatment with an appropriateagent that selects against cells not expressing the selectable marker.Only those cells expressing the selectable marker gene survive and/orgrow under certain conditions. For example, cells that express theintroduced neomycin resistance gene are resistant to the compound G418,while cells that do not express the neo gene marker are killed by G418.If the targeting construct also comprises a screening marker such asGFP, homologous recombination can be identified through screening cellcolonies under a fluorescent light. Cells that have undergone homologousrecombination will have deleted the GFP gene and will not fluoresce.

If a regulated positive selection method is used in identifyinghomologous recombination events, the targeting construct is designed sothat the expression of the selectable marker gene is regulated in amanner such that expression is inhibited following random integrationbut is permitted (derepressed) following homologous recombination. Moreparticularly, the transfected cells are screened for expression of theneo gene, which requires that (1) the cell was successfullyelectroporated, and (2) lac repressor inhibition of neo transcriptionwas relieved by homologous recombination. This method allows for theidentification of transfected cells and homologous recombinants to occurin one step with the addition of a single drug.

Alternatively, a positive-negative selection technique may be used toselect homologous recombinants. This technique involves a process inwhich a first drug is added to the cell population, for example, aneomycin-like drug to select for growth of transfected cells, i.e.positive selection. A second drug, such as FIAU is subsequently added tokill cells that express the negative selection marker, i.e. negativeselection. Cells that contain and express the negative selection markerare killed by a selecting agent, whereas cells that do not contain andexpress the negative selection marker survive. For example, cells withnon-homologous insertion of the construct express HSV thymidine kinaseand therefore are sensitive to the herpes drugs such as gancyclovir(GANC) or FIAU (1-(2-deoxy2-fluoro-B-D-arabinofluranosyl)-5-iodouracil). (see, e.g., Mansour etal., Nature 336:348-352: (1988); Capecchi, Science 244:1288-1292,(1989); Capecchi, Trends in Genet. 5:70-76 (1989)).

Successful recombination may be identified by analyzing the DNA of theselected cells to confirm homologous recombination. Various techniquesknown in the art, such as PCR and/or Southern analysis may be used toconfirm homologous recombination events.

Homologous recombination may also be used to disrupt genes in stemcells, and other cell types, which are not totipotent embryonic stemcells. By way of example, stem cells may be myeloid, lymphoid, or neuralprogenitor and precursor cells. Such transgenic cells may beparticularly useful in the study of CYT28 gene function in individualdevelopmental pathways. Stem cells may be derived from any vertebratespecies, such as mouse, rat, dog, cat, pig, rabbit, human, non-humanprimates and the like.

In cells that are not totipotent, it may be desirable to knock out bothcopies of the target using methods that are known in the art. Forexample, cells comprising homologous recombination at a target locusthat have been selected for expression of a positive selection marker(e.g., Neo^(r)) and screened for non-random integration, can be furtherselected for multiple copies of the selectable marker gene by exposureto elevated levels of the selective agent (e.g., G418). The cells arethen analyzed for homozygosity at the target locus. Alternatively, asecond construct can be generated with a different positive selectionmarker inserted between the two homologous sequences. The two constructscan be introduced into the cell either sequentially or simultaneously,followed by appropriate selection for each of the positive marker genes.The final cell is screened for homologous recombination of both allelesof the target.

Production of Transgenic Animals

Selected cells are then injected into a blastocyst (or other stage ofdevelopment suitable for the purposes of creating a viable animal, suchas, for example, a morula) of an animal (e.g., a mouse) to form chimeras(see e.g., Bradley, A. in Teratocarcinomas and Embryonic Stem Cells: APractical Approach, E. J. Robertson, ed., IRL, Oxford, pp. 113-152(1987)). Alternatively, selected ES cells can be allowed to aggregatewith dissociated mouse embryo cells to form the aggregation chimera. Achimeric embryo can then be implanted into a suitable pseudopregnantfemale foster animal and the embryo brought to term. Chimeric progenyharbouring the homologously recombined DNA in their germ cells can beused to breed animals in which all cells of the animal contain thehomologously recombined DNA. In one embodiment, chimeric progeny miceare used to generate a mouse with a heterozygous disruption in the CYT28gene. Heterozygous transgenic mice can then be mated. It is well knownin the art that typically ¼ of the offspring of such matings will have ahomozygous disruption in the CYT28 gene.

The heterozygous and homozygous transgenic mice can then be compared tonormal, wild-type mice to determine whether disruption of the CYT28 genecauses phenotypic changes, especially pathological changes. For example,heterozygous and homozygous mice may be evaluated for phenotypic changesby physical examination, necropsy, histology, clinical chemistry,complete blood count, body weight, organ weights, and cytologicalevaluation of bone marrow. Phenotypic changes may also comprisebehavioral modifications or abnormalities.

In one embodiment, the phenotype (or phenotype change) associated with adisruption in the CYT28 gene is placed into or stored in a database.Preferably, the database includes: (i) genotypic data (e.g.,identification of the disrupted gene) and (ii) phenotypic data (e.g.,phenotype(s) resulting from the gene disruption) associated with thegenotypic data. The database is preferably electronic. In addition, thedatabase is preferably combined with a search tool so that the databaseis searchable.

Conditional Transgenic Animals

The present invention further contemplates conditional transgenic orknockout animals, such as those produced using recombination methods.Bacteriophage P1 Cre recombinase and flp recombinase from yeast plasmidsare two non-limiting examples of site-specific DNA recombinase enzymesthat cleave DNA at specific target sites (lox P sites for crerecombinase and frt sites for flp recombinase) and catalyze a ligationof this DNA to a second cleaved site. A large number of suitablealternative site-specific recombinases have been described, and theirgenes can be used in accordance with the method of the presentinvention. Such recombinases include the Int recombinase ofbacteriophage λ (with or without Xis) (Weisberg, R. et al., in LambdaII, (Hendrix, R., et al., Eds.), Cold Spring Harbor Press, Cold SpringHarbor, N.Y., pp. 211-50 (1983), herein incorporated by reference); TpnIand the β-lactamase transposons (Mercier, et al., J. Bacteriol.,172:3745-57 (1990)); the Tn3 resolvase (Flanagan & Fennewald J. Molec.Biol., 206:295-304 (1989); Stark, et al., Cell, 58:779-90 (1989)); theyeast recombinases (Matsuzaki, et al., J. Bacteriol., 172:610-18(1990)); the B. subtilis SpoIVC recombinase (Sato, et al., J. Bacteriol.172:1092-98 (1990)); the Flp recombinase (Schwartz & Sadowski, J. Molec.Biol., 205:647-658 (1989); Parsons, et al., J. Biol. Chem., 265:4527-33(1990); Golic & Lindquist, Cell, 59:499-509 (1989); Amin, et al., J.Molec. Biol., 214:55-72 (1990)); the Hin recombinase (Glasgow, et al.,J. Biol. Chem., 264:10072-82 (1989)); immunoglobulin recombinases(Malynn, et al., Cell, 54:453-460 (1988)); and the Cin recombinase(Haffter & Bickle, EMBO J., 7:3991-3996 (1988); Hubner, et al., J.Molec. Biol., 205:493-500 (1989)), all herein incorporated by reference.Such systems are discussed by Echols (J. Biol. Chem. 265:14697-14700(1990)); de Villartay (Nature, 335:170-74 (1988)); Craig, (Ann. Rev.Genet., 22:77-105 (1988)); Poyart-Salmeron, et al., (EMBO J. 8:2425-33(1989)); Hunger-Bertling, et al., (Mol Cell. Biochem., 92:107-16(1990)); and Cregg & Madden (Mol. Gen. Genet., 219:320-23 (1989)), allherein incorporated by reference.

Cre has been purified to homogeneity, and its reaction with the loxPsite has been extensively characterized (Abremski & Hess J. Mol. Biol.259:1509-14 (1984), herein incorporated by reference). Cre protein has amolecular weight of 35,000 and can be obtained commercially from NewEngland Nuclear/Du Pont. The cre gene (which encodes the Cre protein)has been cloned and expressed (Abremski, et al., Cell 32:1301-11 (1983),herein incorporated by reference). The Cre protein mediatesrecombination between two loxP sequences (Sternberg, et al., Cold SpringHarbor Symp. Quant. Biol. 45:297-309 (1981)), which may be present onthe same or different DNA molecule. Because the internal spacer sequenceof the loxP site is asymmetrical, two loxP sites can exhibitdirectionality relative to one another (Hoess & Abremski Proc. Natl.Acad. Sci. U.S.A. 81:1026-29 (1984)). Thus, when two sites on the sameDNA molecule are in a directly repeated orientation, Cre will excise theDNA between the sites (Abremski, et al., Cell 32:1301-11 (1983)).However, if the sites are inverted with respect to each other, the DNAbetween them is not excised after recombination but is simply inverted.Thus, a circular DNA molecule having two loxP sites in directorientation will recombine to produce two smaller circles, whereascircular molecules having two loxP sites in an inverted orientationsimply invert the DNA sequences flanked by the loxP sites. In addition,recombinase action can result in reciprocal exchange of regions distalto the target site when targets are present on separate DNA molecules.

Recombinases have important application for characterizing gene functionin knockout models. When the constructs described herein are used todisrupt CYT28 genes, a fusion transcript can be produced when insertionof the positive selection marker occurs downstream (3′) of thetranslation initiation site of the CYT28 gene. The fusion transcriptcould result in some level of protein expression with unknownconsequence. It has been suggested that insertion of a positiveselection marker gene can affect the expression of nearby genes. Theseeffects may make it difficult to determine gene function after aknockout event since one could not discern whether a given phenotype isassociated with the inactivation of a gene, or the transcription ofnearby genes. Both potential problems are solved by exploitingrecombinase activity. When the positive selection marker is flanked byrecombinase sites in the same orientation, the addition of thecorresponding recombinase will result in the removal of the positiveselection marker. In this way, effects caused by the positive selectionmarker or expression of fusion transcripts are avoided.

In one embodiment, purified recombinase enzyme is provided to the cellby direct microinjection. In another embodiment, recombinase isexpressed from a co-transfected construct or vector in which therecombinase gene is operably linked to a functional promoter. Anadditional aspect of this embodiment is the use of tissue-specific orinducible recombinase constructs that allow the choice of when and whererecombination occurs. One method for practicing the inducible forms ofrecombinase-mediated recombination involves the use of vectors that useinducible or tissue-specific promoters or other gene regulatory elementsto express the desired recombinase activity. The inducible expressionelements are preferably operatively positioned to allow the induciblecontrol or activation of expression of the desired recombinase activity.Examples of such inducible promoters or other gene regulatory elementsinclude, but are not limited to, tetracycline, metallothionine,ecdysone, and other steroid-responsive promoters, rapamycin responsivepromoters, and the like (No, et al., Proc. Natl. Acad. Sci. USA,93:3346-51 (1996); Furth, et al., Proc. Natl. Acad. Sci. USA, 91:9302-6(1994)). Additional control elements that can be used include promotersrequiring specific transcription factors such as viral, promoters.Vectors incorporating such promoters would only express recombinaseactivity in cells that express the necessary transcription factors.

Models for Disease

The cell- and animal-based systems described herein can be utilized asmodels for diseases. Animals of any species, including, but not limitedto, mice, rats, rabbits, guinea pigs, pigs, micro-pigs, goats, andnon-human primates, e.g., baboons, monkeys, and chimpanzees may be usedto generate disease animal models. In addition, cells from humans may beused. These systems may be used in a variety of applications. Suchassays may be utilized as part of screening strategies designed toidentify agents, such as compounds that are capable of amelioratingdisease symptoms. Thus, the animal- and cell-based models may be used toidentify drugs, pharmaceuticals, therapies and interventions that may beeffective in treating disease.

Cell-based systems may be used to identify compounds that may act toameliorate disease symptoms. For example, such cell systems may beexposed to a compound suspected of exhibiting an ability to amelioratedisease symptoms, at a sufficient concentration and for a timesufficient to elicit such an amelioration of disease symptoms in theexposed cells. After exposure, the cells are examined to determinewhether one or more of the disease cellular phenotypes has been alteredto resemble a more normal or more wild-type, non-disease phenotype.

In addition, animal-based disease systems, such as those describedherein, may be used to identify compounds capable of amelioratingdisease symptoms. Such animal models may be used as test substrates forthe identification of drugs, pharmaceuticals, therapies, andinterventions that may be effective in treating a disease or otherphenotypic characteristic of the animal. For example, animal models maybe exposed to a compound or agent suspected of exhibiting an ability toameliorate disease symptoms, at a sufficient concentration and for atime sufficient to elicit such an amelioration of disease symptoms inthe exposed animals. The response of the animals to the exposure may bemonitored by assessing the reversal of disorders associated with thedisease. Exposure may involve treating mother animals during gestationof the model animals described herein, thereby exposing embryos orfetuses to the compound or agent that may prevent or ameliorate thedisease or phenotype. Neonatal, juvenile, and adult animals can also beexposed.

More particularly, using the animal models of the invention, methods ofidentifying agents are provided, in which such agents can be identifiedon the basis of their ability to affect at least one phenotypeassociated with a disruption in a CYT28 gene. In one embodiment, thepresent invention provides a method of identifying agents having aneffect on CYT28 expression or function. The method includes measuring aphysiological response of the animal, for example, to the agent andcomparing the physiological response of such animal to a control animal,wherein the physiological response of the animal comprising a disruptionin a CYT28 gene as compared to the control animal indicates thespecificity of the agent. A “physiological response” is any biologicalor physical parameter of an animal that can be measured. Molecularassays (e.g., gene transcription, protein production and degradationrates), physical parameters (e.g., exercise physiology tests,measurement of various parameters of respiration, measurement of heartrate or blood pressure and measurement of bleeding time), behavioraltesting, and cellular assays (e.g., immunohistochemical assays of cellsurface markers, or the ability of cells to aggregate or proliferate)can be used to assess a physiological response.

The transgenic animals and cells of the present invention may beutilized as models for diseases, disorders, or conditions associatedwith phenotypes relating to a disruption in a CYT28 gene.

In one aspect of the present invention, the transgenic mice comprisinghomozygous disruption in a CYT28 gene exhibit shorter response latenciesto lick their hindpaw, relative to wild-type control mice, indicating anincreased sensitivity to pain. In accordance with this aspect, thetransgenic animals may be used as an in vivo model for evaluating oridentifying treatments for pain.

The present invention provides a unique animal model for testing anddeveloping new treatments relating to the behavioral phenotypes.Analysis of the behavioral phenotype allows for the development of ananimal model useful for testing, for instance, the efficacy of proposedgenetic and pharmacological therapies for human genetic diseases, suchas neurological, neuropsychological, or psychotic illnesses.

A statistical analysis of the various behaviors measured can be carriedout using any conventional statistical program routinely used by thoseskilled in the art (such as, for example, “Analysis of Variance” orANOVA). A “p” value of about 0.05 or less is generally considered to bestatistically significant, although slightly higher p values may stillbe indicative of statistically significant differences. To statisticallyanalyze abnormal behavior, a comparison is made between the behavior ofa transgenic animal (or a group thereof) to the behavior of a wild-typemouse (or a group thereof), typically under certain prescribedconditions. “Abnormal behavior” as used herein refers to behaviorexhibited by an animal having a disruption in the CYT28 gene, e.g.transgenic animal, which differs from an animal without a disruption inthe CYT28 gene, e.g. wild-type mouse. Abnormal behavior consists of anynumber of standard behaviors that can be objectively measured (orobserved) and compared. In the case of comparison, it is preferred thatthe change be statistically significant to confirm that there is indeeda meaningful behavioral difference between the knockout animal and thewild-type control animal. Examples of behaviors that may be measured orobserved include, but are not limited to, ataxia, rapid limb movement,eye movement, breathing, motor activity, cognition, emotional behaviors,social behaviors, hyperactivity, hypersensitivity, anxiety, impairedlearning, abnormal reward behavior, and abnormal social interaction,such as aggression.

A series of tests may be used to measure the behavioral phenotype of theanimal models of the present invention, including neurological andneuropsychological tests to identify abnormal behavior. These tests maybe used to measure abnormal behavior relating to, for example, learningand memory, eating, pain, aggression, sexual reproduction, anxiety,depression, schizophrenia, and drug abuse. (see, e.g., Crawley & Paylor,Hormones and Behavior 31:197-211 (1997)).

The social interaction test involves exposing a mouse to other animalsin a variety of settings. The social behaviors of the animals (e.g.,touching, climbing, sniffing, and mating) are subsequently evaluated.Differences in behaviors can then be statistically analyzed and compared(see, e.g., S. E. File, et al., Pharmacol. Bioch. Behav. 22:941-944(1985); R. R. Holson, Phys. Behav. 37:239-247 (1986)). Examplarybehavioral tests include the following.

The mouse startle response test typically involves exposing the animalto a sensory (typically auditory) stimulus and measuring the startleresponse of the animal (see, e.g., M. A. Geyer, et al., Brain Res. Bull.25:485-498 (1990); Paylor and Crawley, Psychopharmacology 132:169-180(1997)). A pre-pulse inhibition test can also be used, in which thepercent inhibition (from a normal startle response) is measured by“cueing” the animal first with a brief low-intensity pre-pulse prior tothe startle pulse.

The electric shock test generally involves exposure to an electrifiedsurface and measurement of subsequent behaviors such as, for example,motor activity, learning, social behaviors. The behaviors are measuredand statistically analyzed using standard statistical tests. (see, e.g.,G. J. Kant, et al., Pharm. Bioch. Behav. 20:793-797 (1984); N. J.Leidenheimer, et al., Pharmacol. Bioch. Behav. 30:351-355 (1988)).

The tail-pinch or immobilization test involves applying pressure to thetail of the animal and/or restraining the animal's movements. Motoractivity, social behavior, and cognitive behavior are examples of theareas that are measured. (see, e.g., M. Bertolucci D'Angic, et al.,Neurochem. 55:1208-1214 (1990)).

The novelty test generally comprises exposure to a novel environmentand/or novel objects. The animal's motor behavior in the novelenvironment and/or around the novel object are measured andstatistically analyzed. (see, e.g., D. K. Reinstein, et al., Pharm.Bioch. Behav. 17:193-202 (1982); B. Poucet, Behav. Neurosci.103:1009-10016 (1989); R. R. Holson, et al., Phys. Behav. 37:231-238(1986)). This test may be used to detect visual processing deficienciesor defects.

The learned helplessness test involves exposure to stresses, forexample, noxious stimuli, which cannot be affected by the animal'sbehavior. The animal's behavior can be statistically analyzed usingvarious standard statistical tests. (see, e.g., A. Leshner, et al.,Behav. Neural Biol. 26:497-501 (1979)).

Alternatively, a tail suspension test may be used, in which the“immobile” time of the mouse is measured when suspended “upside-down” byits tail. This is a measure of whether the animal struggles, anindicator of depression. In humans, depression is believed to resultfrom feelings of a lack of control over one's life or situation. It isbelieved that a depressive state can be elicited in animals byrepeatedly subjecting them to aversive situations over which they haveno control. A condition of “learned helplessness” is eventually reached,in which the animal will stop trying to change its circumstances andsimply accept its fate. Animals that stop struggling sooner are believedto be more prone to depression. Studies have shown that theadministration of certain antidepressant drugs prior to testingincreases the amount of time that animals struggle before giving up.

The Morris water-maze test comprises learning spatial orientations inwater and subsequently measuring the animal's behaviors, such as, forexample, by counting the number of incorrect choices. The behaviorsmeasured are statistically analyzed using standard statistical tests.(see, e.g., E. M. Spruijt, et al., Brain Res. 527:192-197 (1990)).

Alternatively, a Y-shaped maze may be used (see, e.g., McFarland, D. J.,Pharmacology, Biochemistry and Behavior 32:723-726 (1989); Dellu, F., etal., Neurobiology of Learning and Memory 73:31-48 (2000)). The Y-maze isgenerally believed to be a test of cognitive ability. The dimensions ofeach arm of the Y-maze can be, for example, approximately 40 cm×8 cm×20cm, although other dimensions may be used. Each arm can also have, forexample, sixteen equally spaced photobeams to automatically detectmovement within the arms. At least two different tests can be performedusing such a Y-maze. In a continuous Y-maze paradigm, mice are allowedto explore all three arms of a Y-maze for, e.g., approximately 10minutes. The animals are continuously tracked using photobeam detectiongrids, and the data can be used to measure spontaneous alteration andpositive bias behavior. Spontaneous alteration refers to the naturaltendency of a “normal” animal to visit the least familiar arm of a maze.An alternation is scored when the animal makes two consecutive turns inthe same direction, thus representing a sequence of visits to the leastrecently entered arm of the maze. Position bias determinesegocentrically defined responses by measuring the animal's tendency tofavor turning in one direction over another. Therefore, the test candetect differences in an animal's ability to navigate on the basis ofallocentric or egocentric mechanisms. The two-trial Y-maze memory testmeasures response to novelty and spatial memory based on a free-choiceexploration paradigm. During the first trial (acquisition), the animalsare allowed to freely visit two arms of the Y-maze for, e.g.,approximately 15 minutes. The third arm is blocked off during thistrial. The second trial (retrieval) is performed after an intertrialinterval of, e.g., approximately 2 hours. During the retrieval trial,the blocked arm is opened and the animal is allowed access to all threearms for, e.g., approximately 5 minutes. Data are collected during theretrieval trial and analyzed for the number and duration of visits toeach arm. Because the three arms of the maze are virtually identical,discrimination between novelty and familiarity is dependent on“environmental” spatial cues around the room relative to the position ofeach arm. Changes in arm entry and duration of time spent in the novelarm in a transgenic animal model may be indicative of a role of thatgene in mediating novelty and recognition processes.

The passive avoidance or shuttle box test generally involves exposure totwo or more environments, one of which is noxious, providing a choice tobe learned by the animal. Behavioral measures include, for example,response latency, number of correct responses, and consistency ofresponse. (see, e.g., R. Ader, et al., Psychon. Sci. 26:125-128 (1972);R. R. Holson, Phys. Behav. 37:221-230 (1986)). Alternatively, azero-maze can be used. In a zero-maze, the animals can, for example, beplaced in a closed quadrant of an elevated annular platform having,e.g., 2 open and 2 closed quadrants, and are allowed to explore forapproximately 5 minutes. This paradigm exploits an approach-avoidanceconflict between normal exploratory activity and an aversion to openspaces in rodents. This test measures anxiety levels and can be used toevaluate the effectiveness of anti-anxiolytic drugs. The time spent inopen quadrants versus closed quadrants may be recorded automatically,with, for example, the placement of photobeams at each transition site.

The food avoidance test involves exposure to novel food and objectivelymeasuring, for example, food intake and intake latency. The behaviorsmeasured are statistically analyzed using standard statistical tests.(see, e.g., B. A. Campbell, et al., J. Comp. Physiol. Psychol. 67:15-22(1969)).

The elevated plus-maze test comprises exposure to a maze, without sides,on a platform, the animal's behavior is objectively measured by countingthe number of maze entries and maze learning. The behavior isstatistically analyzed using standard statistical tests. (see, e.g., H.A. Baldwin, et al., Brain Res. Bull, 20:603-606 (1988)).

The stimulant-induced hyperactivity test involves injection of stimulantdrugs (e.g., amphetamines, cocaine, PCP, and the like), and objectivelymeasuring, for example, motor activity, social interactions, cognitivebehavior. The animal's behaviors are statistically analyzed usingstandard statistical tests. (see, e.g., P. B. S. Clarke, et al.,Psychopharmacology 96:511-520 (1988); P. Kuczenski, et al., J.Neuroscience 11:2703-2712 (1991)).

The self-stimulation test generally comprises providing the mouse withthe opportunity to regulate electrical and/or chemical stimuli to itsown brain. Behavior is measured by frequency and pattern ofself-stimulation. Such behaviors are statistically analyzed usingstandard statistical tests. (see, e.g., S. Nassif, et al., Brain Res.,332:247-257 (1985); W. L. Isaac, et al., Behav. Neurosci. 103:345-355(1989)).

The reward test involves shaping a variety of behaviors, e.g., motor,cognitive, and social, measuring, for example, rapidity and reliabilityof behavioral change, and statistically analyzing the behaviorsmeasured. (see, e.g., L. E. Jarrard, et al., Exp. Brain Res. 61:519-530(1986)).

The DRL (differential reinforcement to low rates of responding)performance test involves exposure to intermittent reward paradigms andmeasuring the number of proper responses, e.g., lever pressing. Suchbehavior is statistically analyzed using standard statistical tests.(see, e.g., J. D. Sinden, et al., Behav. Neurosci. 100:320-329 (1986);V. Nalwa, et al., Behav Brain Res. 17:73-76 (1985); and A. J. Nonneman,et al., J. Comp. Physiol. Psych. 95:588-602 (1981)).

The spatial learning test involves exposure to a complex novelenvironment, measuring the rapidity and extent of spatial learning, andstatistically analyzing the behaviors measured. (see, e.g., N. Pitsikas,et al., Pharm. Bioch. Behav. 38:931-934 (1991); B. poucet, et al., BrainRes. 37:269-280 (1990); D. Christie, et al., Brain Res. 37:263-268(1990); and F. Van Haaren, et al., Behav. Neurosci. 102:481-488 (1988)).Alternatively, an open-field (of) test may be used, in which the greaterdistance traveled for a given amount of time is a measure of theactivity level and anxiety of the animal. When the open field is a novelenvironment, it is believed that an approach-avoidance situation iscreated, in which the animal is “torn” between the drive to explore andthe drive to protect itself. Because the chamber is lighted and has noplaces to hide other than the corners, it is expected that a “normal”mouse will spend more time in the comers and around the periphery thanit will in the center where there is no place to hide. “Normal” micewill, however, venture into the central regions as they explore more andmore of the chamber. It can then be extrapolated that especially anxiousmice will spend most of their time in the comers, with relatively littleor no exploration of the central region, whereas bold (i.e., lessanxious) mice will travel a greater distance, showing little preferencefor the periphery versus the central region.

The visual, somatosensory and auditory neglect tests generally compriseexposure to a sensory stimulus, objectively measuring, for example,orientating responses, and statistically analyzing the behaviorsmeasured. (see, e.g., J. M. Vargo, et al., Exp. Neurol. 102:199-209(1988)).

The consummatory behavior test generally comprises feeding and drinking,and objectively measuring quantity of consumption. The behavior measuredis statistically analyzed using standard statistical tests. (see, e.g.,P. J. Fletcher, et al., Psychopharmacol. 102:301-308 (1990); M. G.Corda, et al., Proc. Nat'l Acad. Sci. USA 80:2072-2076 (1983)).

A visual discrimination test can also be used to evaluate the visualprocessing of an animal. One or two similar objects are placed in anopen field and the animal is allowed to explore for about 5-10 minutes.The time spent exploring each object (proximity to, i.e., movementwithin, e.g., about 3-5 cm of the object is considered exploration of anobject) is recorded. The animal is then removed from the open field, andthe objects are replaced by a similar object and a novel object. Theanimal is returned to the open field and the percent time spentexploring the novel object over the old object is measured (again, overabout a 5-10 minute span). “Normal” animals will typically spend ahigher percentage of time exploring the novel object rather than the oldobject. If a delay is imposed between sampling and testing, the memorytask becomes more hippocampal-dependent. If no delay is imposed, thetask is more based on simple visual discrimination. This test can alsobe used for olfactory discrimination, in which the objects (preferably,simple blocks) can be sprayed or otherwise treated to hold an odor. Thistest can also be used to determine if the animal can make gustatorydiscriminations; animals that return to the previously eaten foodinstead of novel food exhibit gustatory neophobia.

A hot plate analgesia test can be used to evaluate an animal'ssensitivity to heat or painful stimuli. For example, a mouse can beplaced on an approximately 55° C. hot plate and the mouse's responselatency (e.g., time to pick up and lick a hind paw) can be recorded.These responses are not reflexes, but rather “higher” responsesrequiring cortical involvement. This test may be used to evaluate anociceptive disorder.

A tail-flick test may also be used to evaluate an animal's sensitivityto heat or painful stimuli. For example, a high-intensity thermalstimulus can be directed to the tail of a mouse and the mouse's responselatency recorded (e.g., the time from onset of stimulation to a rapidflick/withdrawal from the heat source) can be recorded. These responsesare simple nociceptive reflexive responses that are involuntary spinallymediated flexion reflexes. This test may also be used to evaluate anociceptive disorder.

An accelerating rotarod test may be used to measure coordination andbalance in mice. Animals can be, for example, placed on a rod that actslike a rotating treadmill (or rolling log). The rotarod can be made torotate slowly at first and then progressively faster until it reaches aspeed of, e.g., approximately 60 rpm. The mice must continuallyreposition themselves in order to avoid falling off. The animals arepreferably tested in at least three trials, a minimum of 20 minutesapart. Those mice that are able to stay on the rod the longest arebelieved to have better coordination and balance.

A metrazol administration test can be used to screen animals for varyingsusceptibilities to seizures or similar events. For example, a 5 mg/mlsolution of metrazol can be infused through the tail vein of a mouse ata rate of, e.g., approximately 0.375 ml/min. The infusion will cause allmice to experience seizures, followed by death. Those mice that enterthe seizure stage the soonest are believed to be more prone to seizures.Four distinct physiological stages can be recorded: soon after the startof infusion, the mice will exhibit a noticeable “twitch”, followed by aseries of seizures, ending in a final tensing of the body known as“tonic extension”, which is followed by death.

CYT28 Nucleic Acid Sequences and CYT28 Gene Products

The present invention further contemplates use of the CYT28 genesequence to produce CYT28 gene products. CYT28 gene products may includeproteins that represent functionally equivalent gene products. Such anequivalent gene product may contain deletions, additions orsubstitutions of amino acid residues within the amino acid sequenceencoded by the gene sequences described herein, but which result in asilent change, thus producing a functionally equivalent CYT28 geneproduct. Amino acid substitutions may be made on the basis of similarityin polarity, charge, solubility, hydrophobicity, hydrophilicity, and/orthe amphipathic nature of the residues involved.

For example, nonpolar (hydrophobic) amino acids include alanine,leucine, isoleucine, valine, proline, phenylalanine, tryptophan, andmethionine; polar neutral amino acids include glycine, serine,threonine, cysteine, tyrosine, asparagine, and glutamine; positivelycharged (basic) amino acids include arginine, lysine, and histidine; andnegatively charged (acidic) amino acids include aspartic acid andglutamic acid. “Functionally equivalent”, as utilized herein, refers toa protein capable of exhibiting a substantially similar in vivo activityas the endogenous gene products encoded by the CYT28 gene sequences.Alternatively, when utilized as part of an assay, “functionallyequivalent” may refer to peptides capable of interacting with othercellular or extracellular molecules in a manner substantially similar tothe way in which the corresponding portion of the endogenous geneproduct would.

“Percent identity” or “% identity” refers to the percentage of sequencesimilarity found in a comparison of two or more amino acid or nucleicacid sequences. Percent identity can be determined electronically, e.g.,by using the MegAlign.™. program (DNASTAR, Inc., Madison Wis.). TheMegAlign.™. program can create alignments between two or more sequencesaccording to different methods, e.g., the clustal method (see, e.g.,Higgins, D. G. and P. M. Sharp (1988) Gene 73:237-244.). The clustalalgorithm groups sequences into clusters by examining the distancesbetween all pairs. The clusters are aligned pairwise and then in groups.The percentage similarity between two amino acid sequences, e.g.,sequence A and sequence B, is calculated by dividing the length ofsequence A, minus the number of gap residues in sequence A, minus thenumber of gap residues in sequence B, into the sum of the residuematches between sequence A and sequence B, times one hundred. Gaps oflow or of no similarity between the two amino acid sequences are notincluded in determining percentage similarity. Percent identity betweennucleic acid sequences can also be counted or calculated by othermethods known in the art, e.g., the Jotun Hein method (see, e.g., Hein,J. (1990) Methods Enzymol. 183:626-645.). Identity between sequences canalso be determined by other methods known in the art, e.g., by varyinghybridization conditions.

Substantially purified variants, preferably, having at least 90%sequence identity to CYT28 or to a fragment of CYT28 may be used in themethods of identifying agents that modulate CYT28 or alternatively aphenotype associated with CYT28 function as disclosed in the presentinvention.

Isolated and purified polynucleotides which hybridize under stringentconditions to CYT28 or a fragment of CYT28, as well as an isolated andpurified CYT28 polynucleotide complementary to a CYT28 polynucleotideencoding a CYT28 amino acid sequence or a fragment thereof may be usedin methods of identifying agents that modulate CYT28 or alternatively aphenotype associated with CYT28 function as disclosed by the presentinvention.

“Stringent conditions” refers to conditions which permit hybridizationbetween polynucleotides and CYT28 polynucleotides. Stringent conditionscan be defined by salt concentration, the concentration of organicsolvent, e.g., formamide, temperature, and other conditions well knownin the art. In particular, stringency can be increased by reducing theconcentration of salt, increasing the concentration of formamide, orraising the hybridization temperature. For example, stringent saltconcentration will ordinarily be less than about 750 mM NaCl and 75 mMtrisodium citrate, preferably less than about 500 mM NaCl and 50 mMtrisodium citrate, and most preferably less than about 250 mM NaCl and25 mM trisodium citrate. Low stringency hybridization can be obtained inthe absence of organic solvent, e.g., formamide, while high stringencyhybridization can be obtained in the presence of at least about 35%formamide, and most preferably at least about 50% formamide. Stringenttemperature conditions will ordinarily include temperatures of at leastabout 30° C., more preferably of at least about 37° C., and mostpreferably of at least about 42° C. Varying additional parameters, suchas hybridization time, the concentration of detergent, e.g., sodiumdodecyl sulfate (SDS), and the inclusion or exclusion of carrier DNA,are well known to those skilled in the art. Various levels of stringencyare accomplished by combining these various conditions as needed. In apreferred embodiment, hybridization will occur at 30° C. in 750 mM NaCl,75 mM trisodium citrate, and 1% SDS. In a more preferred embodiment,hybridization will occur at 37° C. in 500 mM NaCl, 50 mM trisodiumcitrate, 1% SDS, 35% formamide, and 100 μg/ml denatured salmon sperm DNA(ssDNA). In a most preferred embodiment, hybridization will occur at 42°C. in 250 mM NaCl, 25 mM trisodium citrate, 1% SDS, 50% formamide, and200 μg/ml ssDNA. Useful variations on these conditions will be readilyapparent to those skilled in the art.

Other protein products useful according to the methods of the inventionare peptides derived from or based on the CYT28 gene products producedby recombinant or synthetic means (derived peptides).

CYT28 gene products may be produced by recombinant DNA technology usingtechniques well known in the art. Thus, methods for preparing the genepolypeptides and peptides of the invention by expressing nucleic acidsencoding gene sequences are described herein. Methods that are wellknown to those skilled in the art can be used to construct expressionvectors containing gene protein coding sequences and appropriatetranscriptional/translational control signals. These methods include,for example, in vitro recombinant DNA techniques, synthetic techniquesand in vivo recombination/genetic recombination (see, e.g., Sambrook etal., 1989, supra, and Ausubel et al., 1989, supra). Alternatively, RNAcapable of encoding protein sequences may be chemically synthesizedusing, for example, automated synthesizers (see, e.g. OligonucleotideSynthesis: A Practical Approach, Gait, M. J. ed., IRL Press, Oxford(1984)).

A variety of host-expression vector systems may be utilized to expressthe gene coding sequences of the invention. Such host-expression systemsrepresent vehicles by which the coding sequences of interest may beproduced and subsequently purified, but also represent cells that may,when transformed or transfected with the appropriate nucleotide codingsequences, exhibit the gene protein of the invention in situ. Theseinclude but are not limited to microorganisms such as bacteria (e.g., E.coli, B. subtilis) transformed with recombinant bacteriophage DNA,plasmid DNA or cosmid DNA expression vectors containing gene proteincoding sequences; yeast (e.g. Saccharomyces, Pichia) transformed withrecombinant yeast expression vectors containing the gene protein codingsequences; insect cell systems infected with recombinant virusexpression vectors (e.g., baculovirus) containing the gene proteincoding sequences, plant cell systems infected with recombinant virusexpression vectors (e.g., cauliflower mosaic virus, CaMV; tobacco mosaicvirus, TMV) or transformed with recombinant plasmid expression vectors(e.g., Ti plasmid) containing gene protein coding sequences; ormammalian cell systems (e.g. COS, CHO, BHK, 293, 3T3) harboringrecombinant expression constructs containing promoters derived from thegenome of mammalian cells (e.g., metallothionine promoter) or frommammalian viruses (e.g., the adenovirus late promoter; the vacciniavirus 7.5 K promoter).

In bacterial systems, a number of expression vectors may beadvantageously selected depending upon the use intended for the geneprotein being expressed. For example, when a large quantity of such aprotein is to be produced, for the generation of antibodies or to screenpeptide libraries, for example, vectors that direct the expression ofhigh levels of fusion protein products that are readily purified may bedesirable. Such vectors include, but are not limited to, the E. coliexpression vector pUR278 (Ruther et al., EMBO J., 2:1791-94 (1983)), inwhich the gene protein coding sequence may be ligated individually intothe vector in frame with the lac Z coding region so that a fusionprotein is produced; pIN vectors (Inouye & Inouye, Nucleic Acids Res.,13:3101-09 (1985); Van Heeke et al., J. Biol. Chem., 264:5503-9 (1989));and the like. pGEX vectors may also be used to express foreignpolypeptides as fusion proteins with glutathione S-transferase (GST). Ingeneral, such fusion proteins are soluble and can easily be purifiedfrom lysed cells by adsorption to glutathione-agarose beads followed byelution in the presence of free glutathione. The pGEX vectors aredesigned to include thrombin or factor Xa protease cleavage sites sothat the cloned CYT28 gene protein can be released from the GST moiety.

In a preferred embodiment, full length cDNA sequences are appended within-frame Bam HI sites at the amino terminus and Eco RI sites at thecarboxyl terminus using standard PCR methodologies (Innis et al. (eds)PCR Protocols: A Guide to Methods and Applications, Academic Press, SanDiego (1990)) and ligated into the pGEX-2TK vector (Pharmacia, Uppsala,Sweden). The resulting cDNA construct contains a kinase recognition siteat the amino terminus for radioactive labeling and glutathioneS-transferase sequences at the carboxyl terminus for affinitypurification (Nilsson et al., EMBO J., 4: 1075-80 (1985); Zabeau et al.,EMBO J., 1: 1217-24 (1982)).

In an insect system, Autographa californica nuclear polyhedrosis virus(AcNPV) is used as a vector to express foreign genes. The virus grows inSpodoptera frugiperda cells. The gene coding sequence may be clonedindividually into non-essential regions (for example the polyhedringene) of the virus and placed under control of an AcNPV promoter (forexample the polyhedrin promoter). Successful insertion of gene codingsequence will result in inactivation of the polyhedrin gene andproduction of non-occluded recombinant virus (i.e., virus lacking theproteinaceous coat coded for by the polyhedrin gene). These recombinantviruses are then used to infect Spodoptera frugiperda cells in which theinserted gene is expressed (see, e.g., Smith et al., J. Virol. 46:584-93 (1983); U.S. Pat. No. 4,745,051).

In mammalian host cells, a number of viral-based expression systems maybe utilized. In cases where an adenovirus is used as an expressionvector, the gene coding sequence of interest may be ligated to anadenovirus transcription/translation control complex, e.g., the latepromoter and tripartite leader sequence. This chimeric gene may then beinserted in the adenovirus genome by in vitro or in vivo recombination.Insertion in a non-essential region of the viral genome (e.g., region E1or E3) will result in a recombinant virus that is viable and capable ofexpressing gene protein in infected hosts. (e.g., see Logan et al.,Proc. Natl. Acad. Sci. USA, 81:3655-59 (1984)). Specific initiationsignals may also be required for efficient translation of inserted genecoding sequences. These signals include the ATG initiation codon andadjacent sequences. In cases where an entire gene, including its owninitiation codon and adjacent sequences, is inserted into theappropriate expression vector, no additional translational controlsignals may be needed. However, in cases where only a portion of thegene coding sequence is inserted, exogenous translational controlsignals, including, perhaps, the ATG initiation codon, must be provided.Furthermore, the initiation codon must be in phase with the readingframe of the desired coding sequence to ensure translation of the entireinsert. These exogenous translational control signals and initiationcodons can be of a variety of origins, both natural and synthetic. Theefficiency of expression may be enhanced by the inclusion of appropriatetranscription enhancer elements, transcription terminators, etc. (seeBitter et al., Methods in Enzymol., 153:516-44 (1987)).

In addition, a host cell strain may be chosen that modulates theexpression of the inserted sequences, or modifies and processes the geneproduct in the specific fashion desired. Such modifications (e.g.,glycosylation) and processing (e.g., cleavage) of protein products maybe important for the function of the protein. Different host cells havecharacteristic and specific mechanisms for the post-translationalprocessing and modification of proteins. Appropriate cell lines or hostsystems can be chosen to ensure the correct modification and processingof the foreign protein expressed. To this end, eukaryotic host cellsthat possess the cellular machinery for proper processing of the primarytranscript, glycosylation, and phosphorylation of the gene product maybe used. Such mammalian host cells include but are not limited to CHO,VERO, BHK, HeLa, COS, MDCK, 293, 3T3, W138, etc.

For long-term, high-yield production of recombinant proteins, stableexpression is preferred. For example, cell lines that stably express thegene protein may be engineered. Rather than using expression vectorsthat contain viral origins of replication, host cells can be transformedwith DNA controlled by appropriate expression control elements (e.g.,promoter, enhancer, sequences, transcription terminators,polyadenylation sites, etc.), and a selectable marker. Following theintroduction of the foreign DNA, engineered cells may be allowed to growfor 1-2 days in an enriched media, and then are switched to a selectivemedia. The selectable marker in the recombinant plasmid confersresistance to the selection and allows cells that stably integrate theplasmid into their chromosomes and grow, to form foci, which in turn canbe cloned and expanded into cell lines. This method may advantageouslybe used to engineer cell lines that express the gene protein. Suchengineered cell lines may be particularly useful in screening andevaluation of compounds that affect the endogenous activity of the geneprotein.

In a preferred embodiment, timing and/or quantity of expression of therecombinant protein can be controlled using an inducible expressionconstruct inducible constructs and systems for inducible expression ofrecombinant proteins will be well known to those skilled in the art.Examples of such inducible promoters or other gene regulatory elementsinclude, but are not limited to, tetracycline, metallothionine,ecdysone, and other steroid-responsive promoters, rapamycin responsivepromoters, and the like (No et al., Proc. Natl. Acad. Sci. USA,93:3346-51 (1996); Furth et al., Proc. Natl. Acad. Sci. USA, 91:9302-6(1994)). Additional control elements that can be used include promotersrequiring specific transcription factors such as viral, particularlyHIV, promoters. In one in embodiment, a Tet inducible gene expressionsystem is utilized (Gossen et al., Proc. Natl. Acad. Sci. USA,89:5547-51 (1992); Gossen et al., Science, 268:1766-69 (1995)). TetExpression Systems are based on two regulatory elements derived from thetetracycline-resistance operon of the E. coli Tn10 transposon—thetetracycline repressor protein (TetR) and the tetracycline operatorsequence (tetO) to which TetR binds. Using such a system, expression ofthe recombinant protein is placed under the control of the tetO operatorsequence and transfected or transformed into a host cell. In thepresence of TetR, which is co-transfected into the host cell, expressionof the recombinant protein is repressed due to binding of the TetRprotein to the tetO regulatory element. High-level, regulated geneexpression can then be induced in response to varying concentrations oftetracycline (Tc) or Tc derivatives such as doxycycline (Dox), whichcompete with tetO elements for binding to TetR. Constructs and materialsfor tet inducible gene expression are available commercially fromCLONTECH Laboratories, Inc., Palo Alto, Calif.

When used as a component in an assay system, the gene protein may belabeled, either directly or indirectly, to facilitate detection of acomplex formed between the gene protein and a test substance. Any of avariety of suitable labeling systems may be used including but notlimited to radioisotopes such as ¹²⁵I; enzyme labeling systems thatgenerate a detectable calorimetric signal or light when exposed tosubstrate; and fluorescent labels. Where recombinant DNA technology isused to produce the gene protein for such assay systems, it may beadvantageous to engineer fusion proteins that can facilitate labeling,immobilization and/or detection.

Indirect labeling involves the use of a protein, such as a labeledantibody, which specifically binds to the gene product. Such antibodiesinclude but are not limited to polyclonal, monoclonal, chimeric, singlechain, Fab fragments and fragments produced by a Fab expression library.

Production of Antibodies

Described herein are methods for the production of antibodies capable ofspecifically recognizing one or more epitopes. Such antibodies mayinclude, but are not limited to polyclonal antibodies, monoclonalantibodies (mAbs), humanized or chimeric antibodies, single chainantibodies, Fab fragments, F(ab′)₂ fragments, fragments produced by aFab expression library, anti-idiotypic (anti-Id) antibodies, andepitope-binding fragments of any of the above. Such antibodies may beused, for example, in the detection of a CYT28 gene in a biologicalsample, or, alternatively, as a method for the inhibition of abnormalCYT28 gene activity. Thus, such antibodies may be utilized as part ofdisease treatment methods, and/or may be used as part of diagnostictechniques whereby patients may be tested for abnormal levels of CYT28gene proteins, or for the presence of abnormal forms of such proteins.

For the production of antibodies, various host animals may be immunizedby injection with the CYT28 gene, its expression product or a portionthereof. Such host animals may include but are not limited to rabbits,mice, rats, goats and chickens, to name but a few. Various adjuvants maybe used to increase the immunological response, depending on the hostspecies, including but not limited to Freund's (complete andincomplete), mineral gels such as aluminum hydroxide, surface activesubstances such as lysolecithin, pluronic polyols, polyanions, peptides,oil emulsions, keyhole limpet hemocyanin, dinitrophenol, and potentiallyuseful human adjuvants such as BCG (bacille Calmette-Guerin) andCorynebacterium parvum.

Polyclonal antibodies are heterogeneous populations of antibodymolecules derived from the sera of animals immunized with an antigen,such as a CYT28 gene product, or an antigenic functional derivativethereof. For the production of polyclonal antibodies, host animals suchas those described above, may be immunized by injection with geneproduct supplemented with adjuvants as also described above.

Monoclonal antibodies, which are homogeneous populations of antibodiesto a particular antigen, may be obtained by any technique that providesfor the production of antibody molecules by continuous cell lines inculture. These include, but are not limited to the hybridoma techniqueof Köhler and Milstein, Nature, 256:495-7 (1975); and U.S. Pat. No.4,376,110), the human B-cell hybridoma technique (Kosbor, et al.,Immunology Today, 4:72 (1983); Cote, et al., Proc. Natl. Acad. Sci. USA,80:2026-30 (1983)), and the EBV-hybridoma technique (Cole, et al., inMonoclonal Antibodies And Cancer Therapy, Alan R. Liss, Inc., New York,pp. 77-96 (1985)). Such antibodies may be of any immunoglobulin classincluding IgG, IgM, IgE, IgA, IgD and any subclass thereof. Thehybridoma producing the mAb of this invention may be cultivated in vitroor in vivo. Production of high titers of mAbs in vivo makes this thepresently preferred method of production.

In addition, techniques developed for the production of “chimericantibodies” (Morrison, et al., Proc. Natl. Acad. Sci., 81:6851-6855(1984); Takeda, et al., Nature, 314:452-54 (1985)) by splicing the genesfrom a mouse antibody molecule of appropriate antigen specificitytogether with genes from a human antibody molecule of appropriatebiological activity can be used. A chimeric antibody is a molecule inwhich different portions are derived from different animal species, suchas those having a variable region derived from a murine mAb and a humanimmunoglobulin constant region.

Alternatively, techniques described for the production of single chainantibodies (U.S. Pat. No. 4,946,778; Bird, Science 242:423-26 (1988);Huston, et al., Proc. Natl. Acad. Sci. USA, 85:5879-83 (1988); and Ward,et al., Nature, 334:544-46 (1989)) can be adapted to produce gene-singlechain antibodies. Single chain antibodies are typically formed bylinking the heavy and light chain fragments of the Fv region via anamino acid bridge, resulting in a single chain polypeptide.

Antibody fragments that recognize specific epitopes may be generated byknown techniques. For example, such fragments include but are notlimited to: the F(ab′)₂ fragments that can be produced by pepsindigestion of the antibody molecule and the Fab fragments that can begenerated by reducing the disulfide bridges of the F(ab′)₂ fragments.Alternatively, Fab expression libraries may be constructed (Huse, etal., Science, 246:1275-81 (1989)) to allow rapid and easy identificationof monoclonal Fab fragments with the desired specificity.

Screening Methods

Various animal-derived “preparations,” including cells and tissues, aswell as cell-free extracts, homogenates, fractions and purifiedproteins, may be used to determine whether a particular agent is capableof modulating an activity of a CYT28 or a phenotype associatedtherewith. For example, such preparations may be generated according tomethods well known in the art from the tissues or organs of wild-typeand knockout animals. Wild-type, but not knockout, preparations willcontain endogenous CYT28, as well as the native activities, interactionsand effects of the CYT28. Thus, when knockout and wild-type preparationsare contacted with a test agent in parallel, the ability of the testagent to modulate CYT28, or a phenotype associated therewith, can bedetermined. Agents capable of modulating an activity of a CYT28 or aphenotype associated therewith are identified as those that modulatewild-type, but not knockout, preparations. Modulation may be detected,for example, as the ability of the agent to interact with a preparation,thereby indicating interaction with the gene product itself or a productthereof. Alternatively, the agent may affect a structural, metabolic orbiochemical feature of the preparation, such as enzymatic activity ofthe preparation related to the CYT28. An inclusive discussion of theevents for which modulation by a test agent may be observed is beyondthe scope of this application, but will be well known by those skilledin the art.

The present invention may be employed in a process for screening foragents such as agonists, i.e., agents that bind to and activate CYT28polypeptides, or antagonists, i.e., inhibit the activity or interactionof CYT28 polypeptides with its ligand. Thus, polypeptides of theinvention may also be used to assess the binding of small moleculesubstrates and ligands in, for example, cells, cell-free preparations,chemical libraries, and natural product mixtures as known in the art.Any methods routinely used to identify and screen for agents that canmodulate receptors may be used in accordance with the present invention.

The present invention provides methods for identifying and screening foragents that modulate CYT28 expression or function. More particularly,cells that contain and express CYT28 gene sequences may be used toscreen for therapeutic agents. Such cells may include non-recombinantmonocyte cell lines, such as U937 (ATCC# CRL-1593), THP-1 (ATCC#TIB-202), and P388D1 (ATCC# TIB-63); endothelial cells such as HUVEC'sand bovine aortic endothelial cells (BAEC's); as well as genericmammalian cell lines such as HeLa cells and COS cells, e.g., COS-7(ATCC# CRL-1651). Further, such cells may include recombinant,transgenic cell lines. For example, the transgenic mice of the inventionmay be used to generate cell lines, containing one or more cell typesinvolved in a disease, that can be used as cell culture models for thatdisorder. While cells, tissues, and primary cultures derived from thedisease transgenic animals of the invention may be utilized, thegeneration of continuous cell lines is preferred. For examples oftechniques that may be used to derive a continuous cell line from thetransgenic animals, see Small, et al., Mol. Cell Biol., 5:642-48 (1985).

CYT28 gene sequences may be introduced into and overexpressed in, thegenome of the cell of interest. In order to overexpress a CYT28 genesequence, the coding portion of the CYT28 gene sequence may be ligatedto a regulatory sequence that is capable of driving gene expression inthe cell type of interest. Such regulatory regions will be well known tothose of skill in the art, and may be utilized in the absence of undueexperimentation. CYT28 gene sequences may also be disrupted orunderexpressed. Cells having CYT28 gene disruptions or underexpressedCYT28 gene sequences may be used, for example, to screen for agentscapable of affecting alternative pathways that compensate for any lossof function attributable to the disruption or underexpression.

In vitro systems may be designed to identify compounds capable ofbinding the CYT28 gene products. Such compounds may include, but are notlimited to, peptides made of D- and/or L-configuration amino acids (in,for example, the form of random peptide libraries; (see e.g., Lam, etal., Nature, 354:82-4 (1991)), phosphopeptides (in, for example, theform of random or partially degenerate, directed phosphopeptidelibraries; see, e.g., Songyang, et al., Cell, 72:767-78 (1993)),antibodies, and small organic or inorganic molecules. Compoundsidentified may be useful, for example, in modulating the activity ofCYT28 gene proteins, preferably mutant CYT28 gene proteins; elaboratingthe biological function of the CYT28 gene protein; or screening forcompounds that disrupt normal CYT28 gene interactions or themselvesdisrupt such interactions.

The principle of the assays used to identify compounds that bind to theCYT28 gene protein involves preparing a reaction mixture of the CYT28gene protein and the test compound under conditions and for a timesufficient to allow the two components to interact and bind, thusforming a complex that can be removed and/or detected in the reactionmixture. These assays can be conducted in a variety of ways. Forexample, one method to conduct such an assay would involve anchoring theCYT28 gene protein or the test substance onto a solid phase anddetecting target protein/test substance complexes anchored on the solidphase at the end of the reaction. In one embodiment of such a method,the CYT28 gene protein may be anchored onto a solid surface, and thetest compound, which is not anchored, may be labeled, either directly orindirectly.

In practice, microtitre plates are conveniently utilized. The anchoredcomponent may be immobilized by non-covalent or covalent attachments.Non-covalent attachment may be accomplished simply by coating the solidsurface with a solution of the protein and drying. Alternatively, animmobilized antibody, preferably a monoclonal antibody, specific for theprotein may be used to anchor the protein to the solid surface. Thesurfaces may be prepared in advance and stored.

In order to conduct the assay, the nonimmobilized component is added tothe coated surface containing the anchored component. After the reactionis complete, unreacted components are removed (e.g., by washing) underconditions such that any complexes formed will remain immobilized on thesolid surface. The detection of complexes anchored on the solid surfacecan be accomplished in a number of ways. Where the previouslynonimmobilized component is pre-labeled, the detection of labelimmobilized on the surface indicates that complexes were formed. Wherethe previously nonimmobilized component is not pre-labeled, an indirectlabel can be used to detect complexes anchored on the surface; e.g.,using a labeled antibody specific for the previously nonimmobilizedcomponent (the antibody, in turn, may be directly labeled or indirectlylabeled with a labeled anti-Ig antibody).

Alternatively, a reaction can be conducted in a liquid phase, thereaction products separated from unreacted components, and complexesdetected; e.g., using an immobilized antibody specific for CYT28 geneproduct or the test compound to anchor any complexes formed in solution,and a labeled antibody specific for the other component of the possiblecomplex to detect anchored complexes.

Compounds that are shown to bind to a particular CYT28 gene productthrough one of the methods described above can be further tested fortheir ability to elicit a biochemical response from the CYT28 geneprotein. Agonists, antagonists and/or inhibitors of the expressionproduct can be identified utilizing assays well known in the art.

Antisense, Ribozymes, and Antibodies

Other agents that may be used as therapeutics include the CYT28 gene,its expression product(s) and functional fragments thereof.Additionally, agents that reduce or inhibit mutant CYT28 gene activitymay be used to ameliorate disease symptoms. Such agents includeantisense, ribozyme, and triple helix molecules. Techniques for theproduction and use of such molecules are well known to those of skill inthe art.

Anti-sense RNA and DNA molecules act to directly block the translationof mRNA by hybridizing to targeted mRNA and preventing proteintranslation. With respect to antisense DNA, oligodeoxyribonucleotidesderived from the translation initiation site, e.g., between the −10 and+10 regions of the CYT28 gene nucleotide sequence of interest, arepreferred.

Ribozymes are enzymatic RNA molecules capable of catalyzing the specificcleavage of RNA. The mechanism of ribozyme action involvessequence-specific hybridization of the ribozyme molecule tocomplementary target RNA, followed by an endonucleolytic cleavage. Thecomposition of ribozyme molecules must include one or more sequencescomplementary to the CYT28 gene mRNA, and must include the well knowncatalytic sequence responsible for mRNA cleavage. For this sequence, seeU.S. Pat. No. 5,093,246, which is incorporated by reference herein inits entirety. As such within the scope of the invention are engineeredhammerhead motif ribozyme molecules that specifically and efficientlycatalyze endonucleolytic cleavage of RNA sequences encoding CYT28 geneproteins.

Specific ribozyme cleavage sites within any potential RNA target areinitially identified by scanning the molecule of interest for ribozymecleavage sites that include the following sequences, GUA, GUU and GUC.Once identified, short RNA sequences of between 15 and 20ribonucleotides corresponding to the region of the CYT28 gene containingthe cleavage site may be evaluated for predicted structural features,such as secondary structure, that may render the oligonucleotidesequence unsuitable. The suitability of candidate sequences may also beevaluated by testing their accessibility to hybridization withcomplementary oligonucleotides, using ribonuclease protection assays.

Nucleic acid molecules to be used in triple helix formation for theinhibition of transcription should be single stranded and composed ofdeoxyribonucleotides. The base composition of these oligonucleotidesmust be designed to promote triple helix formation via Hoogsteen basepairing rules, which generally require sizeable stretches of eitherpurines or pyrimidines to be present on one strand of a duplex.Nucleotide sequences may be pyrimidine-based, which will result in TATand CGC triplets across the three associated strands of the resultingtriple helix. The pyrimidine-rich molecules provide base complementarityto a purine-rich region of a single strand of the duplex in a parallelorientation to that strand. In addition, nucleic acid molecules may bechosen that are purine-rich, for example, containing a stretch of Gresidues. These molecules will form a triple helix with a DNA duplexthat is rich in GC pairs, in which the majority of the purine residuesare located on a single strand of the targeted duplex, resulting in GGCtriplets across the three strands in the triplex.

Alternatively, the potential sequences that can be targeted for triplehelix formation may be increased by creating a so called “switchback”nucleic acid molecule. Switchback molecules are synthesized in analternating 5′-3′, 3′-5′ manner, such that they base pair with first onestrand of a duplex and then the other, eliminating the necessity for asizeable stretch of either purines or pyrimidines to be present on onestrand of a duplex.

It is possible that the antisense, ribozyme, and/or triple helixmolecules described herein may reduce or inhibit the transcription(triple helix) and/or translation (antisense, ribozyme) of mRNA producedby both normal and mutant CYT28 gene alleles. In order to ensure thatsubstantially normal levels of CYT28 gene activity are maintained,nucleic acid molecules that encode and express CYT28 polypeptidesexhibiting normal activity may be introduced into cells that do notcontain sequences susceptible to whatever antisense, ribozyme, or triplehelix treatments are being utilized. Alternatively, it may be preferableto coadminister normal CYT28 protein into the cell or tissue in order tomaintain the requisite level of cellular or tissue CYT28 gene activity.

Anti-sense RNA and DNA, ribozyme, and triple helix molecules of theinvention may be prepared by any method known in the art for thesynthesis of DNA and RNA molecules. These include techniques forchemically synthesizing oligodeoxyribonucleotides andoligoribonucleotides well known in the art such as for example solidphase phosphoramidite chemical synthesis. Alternatively, RNA moleculesmay be generated by in vitro and in vivo transcription of DNA sequencesencoding the antisense RNA molecule. Such DNA sequences may beincorporated into a wide variety of vectors that incorporate suitableRNA polymerase promoters such as the T7 or SP6 polymerase promoters.Alternatively, antisense cDNA constructs that synthesize antisense RNAconstitutively or inducibly, depending on the promoter used, can beintroduced stably into cell lines.

Various well-known modifications to the DNA molecules may be introducedas a means of increasing intracellular stability and half-life. Possiblemodifications include but are not limited to the addition of flankingsequences of ribonucleotides or deoxyribonucleotides to the 5′ and/or 3′ends of the molecule or the use of phosphorothioate or 2′ O-methylrather than phosphodiesterase linkages within theoligodeoxyribonucleotide backbone.

Antibodies that are both specific for CYT28 protein, and in particular,the mutant CYT28 protein, and interfere with its activity may be used toinhibit mutant CYT28 gene function. Such antibodies may be generatedagainst the proteins themselves or against peptides corresponding toportions of the proteins using standard techniques known in the art andas also described herein. Such antibodies include but are not limited topolyclonal, monoclonal, Fab fragments, single chain antibodies, chimericantibodies, antibody mimetics, etc.

In instances where the CYT28 protein is intracellular and wholeantibodies are used, internalizing antibodies may be preferred. However,lipofectin liposomes may be used to deliver the antibody or a fragmentof the Fab region that binds to the CYT28 gene epitope into cells. Wherefragments of the antibody are used, the smallest inhibitory fragmentthat binds to the target or expanded target protein's binding domain ispreferred. For example, peptides having an amino acid sequencecorresponding to the domain of the variable region of the antibody thatbinds to the CYT28 protein may be used. Such peptides may be synthesizedchemically or produced via recombinant DNA technology using methods wellknown in the art (see, e.g., Creighton, Proteins: Structures andMolecular Principles (1984) W.H. Freeman, New York 1983, supra; andSambrook, et al., 1989, supra). Alternatively, single chain neutralizingantibodies that bind to intracellular CYT28 gene epitopes may also beadministered. Such single chain antibodies may be administered, forexample, by expressing nucleotide sequences encoding single-chainantibodies within the target cell population by utilizing, for example,techniques such as those described in Marasco, et al., Proc. Natl. Acad.Sci. USA, 90:7889-93 (1993).

RNA sequences encoding CYT28 protein may be directly administered to apatient exhibiting disease symptoms, at a concentration sufficient toproduce a level of CYT28 protein such that disease symptoms areameliorated. Patients may be treated by gene replacement therapy. One ormore copies of a normal CYT28 gene, or a portion of the gene thatdirects the production of a normal CYT28 protein with CYT28 genefunction, may be inserted into cells using vectors that include, but arenot limited to adenovirus, adeno-associated virus, and retrovirusvectors, in addition to other particles that introduce DNA into cells,such as liposomes. Additionally, techniques such as those describedabove may be utilized for the introduction of normal CYT28 genesequences into human cells.

Cells, preferably autologous cells, containing normal CYT28 geneexpressing gene sequences may then be introduced or reintroduced intothe patient at positions that allow for the amelioration of diseasesymptoms.

Pharmaceutical Compositions, Effective Dosages, and Routes ofAdministration

The identified compounds that inhibit target mutant gene expression,synthesis and/or activity can be administered to a patient attherapeutically effective doses to treat or ameliorate the disease. Atherapeutically effective dose refers to that amount of the compoundsufficient to result in amelioration of symptoms of the disease.

Toxicity and therapeutic efficacy of such compounds can be determined bystandard pharmaceutical procedures in cell cultures or experimentalanimals, e.g., for determining the LD₅₀ (the dose lethal to 50% of thepopulation) and the ED₅₀ (the dose therapeutically effective in 50% ofthe population). The dose ratio between toxic and therapeutic effects isthe therapeutic index and it can be expressed as the ratio LD₅₀/ED₅₀.Compounds that exhibit large therapeutic indices are preferred. Whilecompounds that exhibit toxic side effects may be used, care should betaken to design a delivery system that targets such compounds to thesite of affected tissue in order to minimize potential damage touninfected cells and, thereby, reduce side effects.

The data obtained from the cell culture assays and animal studies can beused in formulating a range of dosage for use in humans. The dosage ofsuch compounds lies preferably within a range of circulatingconcentrations that include the ED₅₀ with little or no toxicity. Thedosage may vary within this range depending upon the dosage formemployed and the route of administration utilized. For any compound usedin the method of the invention, the therapeutically effective dose canbe estimated initially from cell culture assays. A dose may beformulated in animal models to achieve a circulating plasmaconcentration range that includes the IC₅₀ (i.e., the concentration ofthe test compound that achieves a half-maximal inhibition of symptoms)as determined in cell culture. Such information can be used to moreaccurately determine useful doses in humans. Levels in plasma may bemeasured, for example, by high performance liquid chromatography.

Pharmaceutical compositions for use in accordance with the presentinvention may be formulated in conventional manner using one or morephysiologically acceptable carriers or excipients. Thus, the compoundsand their physiologically acceptable salts and solvates may beformulated for administration by inhalation or insufflation (eitherthrough the mouth or the nose) or oral, buccal, parenteral, topical,subcutaneous, intraperitoneal, intraveneous, intrapleural, intraoccular,intraarterial, or rectal administration. It is also contemplated thatpharmaceutical compositions may be administered with other products thatpotentiate the activity of the compound and optionally, may includeother therapeutic ingredients.

For oral administration, the pharmaceutical compositions may take theform of, for example, tablets or capsules prepared by conventional meanswith pharmaceutically acceptable excipients such as binding agents(e.g., pregelatinised maize starch, polyvinylpyrrolidone orhydroxypropyl methylcellulose); fillers (e.g., lactose, microcrystallinecellulose or calcium hydrogen phosphate); lubricants (e.g., magnesiumstearate, talc or silica); disintegrants (e.g., potato starch or sodiumstarch glycolate); or wetting agents (e.g., sodium lauryl sulphate). Thetablets may be coated by methods well known in the art. Liquidpreparations for oral administration may take the form of, for example,solutions, syrups or suspensions, or they may be presented as a dryproduct for constitution with water or other suitable vehicle beforeuse. Such liquid preparations may be prepared by conventional means withpharmaceutically acceptable additives such as suspending agents (e.g.,sorbitol syrup, cellulose derivatives or hydrogenated edible fats);emulsifying agents (e.g., lecithin or acacia); non-aqueous vehicles(e.g., almond oil, oily esters, ethyl alcohol or fractionated vegetableoils); and preservatives (e.g., methyl or propyl-p-hydroxybenzoates orsorbic acid). The preparations may also contain buffer salts, flavoring,coloring and sweetening agents as appropriate.

Preparations for oral administration may be suitably formulated to givecontrolled release of the active compound.

For buccal administration the compositions may take the form of tabletsor lozenges formulated in conventional manner.

For administration by inhalation, the compounds for use according to thepresent invention are conveniently delivered in the form of an aerosolspray presentation from pressurized packs or a nebuliser, with the useof a suitable propellant, e.g., dichlorodifluoromethane,trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide orother suitable gas. In the case of a pressurized aerosol the dosage unitmay be determined by providing a valve to deliver a metered amount.Capsules and cartridges of e.g. gelatin for use in an inhaler orinsufflator may be formulated containing a powder mix of the compoundand a suitable powder base such as lactose or starch.

The compounds may be formulated for parenteral administration byinjection, e.g., by bolus injection or continuous infusion. Formulationsfor injection may be presented in unit dosage form, e.g., in ampoules orin multi-dose containers, with an added preservative. The compositionsmay take such forms as suspensions, solutions or emulsions in oily oraqueous vehicles, and may contain formulatory agents such as suspending,stabilizing and/or dispersing agents. Alternatively, the activeingredient may be in powder form for constitution with a suitablevehicle, e.g., sterile pyrogen-free water, before use.

The compounds may also be formulated in rectal compositions such assuppositories or retention enemas, e.g., containing conventionalsuppository bases such as cocoa butter or other glycerides. Oralingestion is possibly the easiest method of taking any medication. Sucha route of administration, is generally simple and straightforward andis frequently the least inconvenient or unpleasant route ofadministration from the patient's point of view. However, this involvespassing the material through the stomach, which is a hostile environmentfor many materials, including proteins and other biologically activecompositions. As the acidic, hydrolytic and proteolytic environment ofthe stomach has evolved efficiently to digest proteinaceous materialsinto amino acids and oligopeptides for subsequent anabolism, it ishardly surprising that very little or any of a wide variety ofbiologically active proteinaceous material, if simply taken orally,would survive its passage through the stomach to be taken up by the bodyin the small intestine. The result, is that many proteinaceousmedicaments must be taken in through another method, such asparenterally, often by subcutaneous, intramuscular or intravenousinjection.

Pharmaceutical compositions may also include various buffers (e.g.,Tris, acetate, phosphate), solubilizers (e.g., Tween, Polysorbate),carriers such as human serum albumin, preservatives (thimerosol, benzylalcohol) and anti-oxidants such as ascorbic acid in order to stabilizepharmaceutical activity. The stabilizing agent may be a detergent, suchas tween-20, tween-80, NP-40 or Triton X-100. EBP may also beincorporated into particulate preparations of polymeric compounds forcontrolled delivery to a patient over an extended period of time. A moreextensive survey of components in pharmaceutical compositions is foundin Remington's Pharmaceutical Sciences, 18th ed., A. R. Gennaro, ed.,Mack Publishing, Easton, Pa. (1990).

In addition to the formulations described previously, the compounds mayalso be formulated as a depot preparation. Such long acting formulationsmay be administered by implantation (for example, subcutaneously orintramuscularly) or by intramuscular injection. Thus, for example, thecompounds may be formulated with suitable polymeric or hydrophobicmaterials (for example as an emulsion in an acceptable oil) or ionexchange resins, or as sparingly soluble derivatives, for example, as asparingly soluble salt.

The compositions may, if desired, be presented in a pack or dispenserdevice that may contain one or more unit dosage forms containing theactive ingredient. The pack may for example comprise metal or plasticfoil, such as a blister pack. The pack or dispenser device may beaccompanied by instructions for administration.

Diagnostics

A variety of methods may be employed to diagnose disease conditionsassociated with the CYT28 gene. Specifically, reagents may be used, forexample, for the detection of the presence of CYT28 gene mutations, orthe detection of either over- or under- expression of CYT28 gene mRNA.

According to the diagnostic and prognostic method of the presentinvention, alteration of the wild-type CYT28 gene locus is detected. Inaddition, the method can be performed by detecting the wild-type CYT28gene locus and confirming the lack of a predisposition or neoplasia.“Alteration of a wild-type gene” encompasses all forms of mutationsincluding deletions, insertions and point mutations in the coding andnoncoding regions. Deletions may be of the entire gene or only a portionof the gene. Point mutations may result in stop codons, frameshiftmutations or amino acid substitutions. Somatic mutations are those thatoccur only in certain tissues, e.g., in tumor tissue, and are notinherited in the germline. Germline mutations can be found in any of abody's tissues and are inherited. If only a single allele is somaticallymutated, an early neoplastic state may be indicated. However, if bothalleles are mutated, then a late neoplastic state may be indicated. Thefinding of gene mutations thus provides both diagnostic and prognosticinformation. A CYT28 gene allele that is not deleted (e.g., that foundon the sister chromosome to a chromosome carrying a CYT28 gene deletion)can be screened for other mutations, such as insertions, smalldeletions, and point mutations. Mutations found in tumor tissues may belinked to decreased expression of the CYT28 gene product. However,mutations leading to non-functional gene products may also be linked toa cancerous state. Point mutational events may occur in regulatoryregions, such as in the promoter of the gene, leading to loss ordiminution of expression of the mRNA. Point mutations may also abolishproper RNA processing, leading to loss of expression of the CYT28 geneproduct, or a decrease in mRNA stability or translation efficiency.

One test available for detecting mutations in a candidate locus is todirectly compare genomic target sequences from cancer patients withthose from a control population. Alternatively, one could sequencemessenger RNA after amplification, e.g., by PCR, thereby eliminating thenecessity of determining the exon structure of the candidate gene.Mutations from cancer patients falling outside the coding region of theCYT28 gene can be detected by examining the non-coding regions, such asintrons and regulatory sequences near or within the CYT28 gene. An earlyindication that mutations in noncoding regions are important may comefrom Northern blot experiments that reveal messenger RNA molecules ofabnormal size or abundance in cancer patients as compared to controlindividuals.

The methods described herein may be performed, for example, by utilizingpre-packaged diagnostic kits comprising at least one specific genenucleic acid or anti-gene antibody reagent described herein, which maybe conveniently used, e.g., in clinical settings, to diagnose patientsexhibiting disease symptoms or at risk for developing disease.

Any cell type or tissue, including brain, cortex, subcortical region,cerebellum, brainstem, olfactory bulb, spinal cord, eye, Harderiangland, heart, lung, liver, pancreas, kidney, spleen, thymus, lymphnodes, bone marrow, skin, gallbladder, urinary bladder, pituitary gland,adrenal gland, salivary gland, skeletal muscle, tongue, stomach, smallintestine, large intestine, cecum, testis, epididymis, seminal vesicle,coagulating gland, prostate gland, ovary, uterus and white fat, in whichthe gene is expressed may be utilized in the diagnostics describedbelow.

DNA or RNA from the cell type or tissue to be analyzed may easily beisolated using procedures that are well known to those in the art.Diagnostic procedures may also be performed in situ directly upon tissuesections (fixed and/or frozen) of patient tissue obtained from biopsiesor resections, such that no nucleic acid purification is necessary.Nucleic acid reagents may be used as probes and/or primers for such insitu procedures (see, for example, Nuovo, PCR In Situ Hybridization:Protocols and Applications, Raven Press, N.Y. (1992)).

Gene nucleotide sequences, either RNA or DNA, may, for example, be usedin hybridization or amplification assays of biological samples to detectdisease-related gene structures and expression. Such assays may include,but are not limited to, Southern or Northern analyses, restrictionfragment length polymorphism assays, single stranded conformationalpolymorphism analyses, in situ hybridization assays, and polymerasechain reaction analyses. Such analyses may reveal both quantitativeaspects of the expression pattern of the gene, and qualitative aspectsof the gene expression and/or gene composition. That is, such aspectsmay include, for example, point mutations, insertions, deletions,chromosomal rearrangements, and/or activation or inactivation of geneexpression.

Preferred diagnostic methods for the detection of gene-specific nucleicacid molecules may involve for example, contacting and incubatingnucleic acids, derived from the cell type or tissue being analyzed, withone or more labeled nucleic acid reagents under conditions favorable forthe specific annealing of these reagents to their complementarysequences within the nucleic acid molecule of interest. Preferably, thelengths of these nucleic acid reagents are at least 9 to 30 nucleotides.After incubation, all non-annealed nucleic acids are removed from thenucleic acid:fingerprint molecule hybrid. The presence of nucleic acidsfrom the fingerprint tissue that have hybridized, if any such moleculesexist, is then detected. Using such a detection scheme, the nucleic acidfrom the tissue or cell type of interest may be immobilized, forexample, to a solid support such as a membrane, or a plastic surfacesuch as that on a microtitre plate or polystyrene beads. In this case,after incubation, non-annealed, labeled nucleic acid reagents are easilyremoved. Detection of the remaining, annealed, labeled nucleic acidreagents is accomplished using standard techniques well-known to thosein the art.

Alternative diagnostic methods for the detection of gene-specificnucleic acid molecules may involve their amplification, e.g., by PCR(the experimental embodiment set forth in Mullis U.S. Pat. No. 4,683,202(1987)), ligase chain reaction (Barany, Proc. Natl. Acad. Sci. USA,88:189-93 (1991)), self sustained sequence replication (Guatelli, etal., Proc. Natl. Acad. Sci. USA, 87:1874-78 (1990)), transcriptionalamplification system (Kwoh, et al., Proc. Natl. Acad. Sci. USA,86:1173-77 (1989)), Q-Beta Replicase (Lizardi et al., Bio/Technology,6:1197 (1988)), or any other nucleic acid amplification method, followedby the detection of the amplified molecules using techniques well knownto those of skill in the art. These detection schemes are especiallyuseful for the detection of nucleic acid molecules if such molecules arepresent in very low numbers.

In one embodiment of such a detection scheme, a cDNA molecule isobtained from an RNA molecule of interest (e.g., by reversetranscription of the RNA molecule into cDNA). Cell types or tissues fromwhich such RNA may be isolated include any tissue in which wild-typefingerprint gene is known to be expressed, including, but not limited,to brain, cortex, subcortical region, cerebellum, brainstem, olfactorybulb, spinal cord, eye, Harderian gland, heart, lung, liver, pancreas,kidney, spleen, thymus, lymph nodes, bone marrow, skin, gallbladder,urinary bladder, pituitary gland, adrenal gland, salivary gland,skeletal muscle, tongue, stomach, small intestine, large intestine,cecum, testis, epididymis, seminal vesicle, coagulating gland, prostategland, ovary, uterus and white fat. A sequence within the cDNA is thenused as the template for a nucleic acid amplification reaction, such asa PCR amplification reaction, or the like. The nucleic acid reagentsused as synthesis initiation reagents (e.g., primers) in the reversetranscription and nucleic acid amplification steps of this method may bechosen from among the gene nucleic acid reagents described herein. Thepreferred lengths of such nucleic acid reagents are at least 15-30nucleotides. For detection of the amplified product, the nucleic acidamplification may be performed using radioactively or non-radioactivelylabeled nucleotides. Alternatively, enough amplified product may be madesuch that the product may be visualized by standard ethidium bromidestaining or by utilizing any other suitable nucleic acid stainingmethod.

Antibodies directed against wild-type or mutant gene peptides may alsobe used as disease diagnostics and prognostics. Such diagnostic methods,may be used to detect abnormalities in the level of gene proteinexpression, or abnormalities in the structure and/or tissue, cellular,or subcellular location of fingerprint gene protein. Structuraldifferences may include, for example, differences in the size,electronegativity, or antigenicity of the mutant fingerprint geneprotein relative to the normal fingerprint gene protein.

Protein from the tissue or cell type to be analyzed may easily bedetected or isolated using techniques that are well known to those ofskill in the art, including but not limited to western blot analysis.For a detailed explanation of methods for carrying out western blotanalysis, see Sambrook, et al. (1989) supra, at Chapter 18. The proteindetection and isolation methods employed herein may also be such asthose described in Harlow and Lane, for example, (Antibodies: ALaboratory Manual, Cold Spring Harbor Laboratory Press, Cold SpringHarbor, N.Y. (1988)).

Preferred diagnostic methods for the detection of wild-type or mutantgene peptide molecules may involve, for example, immunoassays whereinfingerprint gene peptides are detected by their interaction with ananti-fingerprint gene-specific peptide antibody.

For example, antibodies, or fragments of antibodies useful in thepresent invention may be used to quantitatively or qualitatively detectthe presence of wild-type or mutant gene peptides. This can beaccomplished, for example, by immunofluorescence techniques employing afluorescently labeled antibody (see below) coupled with lightmicroscopic, flow cytometric, or fluorimetric detection. Such techniquesare especially preferred if the fingerprint gene peptides are expressedon the cell surface.

The antibodies (or fragments thereof) useful in the present inventionmay, additionally, be employed histologically, as in immunofluorescenceor immunoelectron microscopy, for in situ detection of fingerprint genepeptides. In situ detection may be accomplished by removing ahistological specimen from a patient, and applying thereto a labeledantibody of the present invention. The antibody (or fragment) ispreferably applied by overlaying the labeled antibody (or fragment) ontoa biological sample. Through the use of such a procedure, it is possibleto determine not only the presence of the fingerprint gene peptides, butalso their distribution in the examined tissue. Using the presentinvention, those of ordinary skill will readily perceive that any of awide variety of histological methods (such as staining procedures) canbe modified in order to achieve such in situ detection.

Immunoassays for wild-type, mutant, or expanded fingerprint genepeptides typically comprise incubating a biological sample, such as abiological fluid, a tissue extract, freshly harvested cells, or cellsthat have been incubated in tissue culture, in the presence of adetectably labeled antibody capable of identifying fingerprint genepeptides, and detecting the bound antibody by any of a number oftechniques well known in the art.

The biological sample may be brought in contact with and immobilizedonto a solid phase support or carrier such as nitrocellulose, or othersolid support that is capable of immobilizing cells, cell particles orsoluble proteins. The support may then be washed with suitable buffersfollowed by treatment with the detectably labeled gene-specificantibody. The solid phase support may then be washed with the buffer asecond time to remove unbound antibody. The amount of bound label onsolid support may then be detected by conventional means.

The terms “solid phase support or carrier” are intended to encompass anysupport capable of binding an antigen or an antibody. Well-knownsupports or carriers include glass, polystyrene, polypropylene,polyethylene, dextran, nylon, amylases, natural and modified celluloses,polyacrylamides, gabbros, and magnetite. The nature of the carrier canbe either soluble to some extent or insoluble for the purposes of thepresent invention. The support material may have virtually any possiblestructural configuration so long as the coupled molecule is capable ofbinding to an antigen or antibody. Thus, the support configuration maybe spherical, as in a bead, or cylindrical, as in the inside surface ofa test tube, or the external surface of a rod. Alternatively, thesurface may be flat such as a sheet, test strip, etc. Preferred supportsinclude polystyrene beads. Those skilled in the art will know many othersuitable carriers for binding antibody or antigen, or will be able toascertain the same by use of routine experimentation.

The binding activity of a given lot of anti-wild-type or -mutantfingerprint gene peptide antibody may be determined according to wellknown methods. Those skilled in the art will be able to determineoperative and optimal assay conditions for each determination byemploying routine experimentation.

One of the ways in which the gene peptide-specific antibody can bedetectably labeled is by linking the same to an enzyme and using it inan enzyme immunoassay (EIA) (Voller, Ric Clin Lab, 8:289-98 (1978) [“TheEnzyme Linked Immunosorbent Assay (ELISA)”, Diagnostic Horizons 2:1-7,1978, Microbiological Associates Quarterly Publication, Walkersville,Md.]; Voller, et al., J. Clin. Pathol., 31:507-20 (1978); Butler, Meth.Enzymol., 73:482-523 (1981); Maggio (ed.), Enzyme Immunoassay, CRCPress, Boca Raton, Fla. (1980); Ishikawa, et al., (eds.) EnzymeImmunoassay, Igaku-Shoin, Tokyo (1981)). The enzyme that is bound to theantibody will react with an appropriate substrate, preferably achromogenic substrate, in such a manner as to produce a chemical moietythat can be detected, for example, by spectrophotometric, fluorimetricor by visual means. Enzymes that can be used to detectably label theantibody include, but are not limited to, malate dehydrogenase,staphylococcal nuclease, delta-5-steroid isomerase, yeast alcoholdehydrogenase, alpha-glycerophosphate, dehydrogenase, triose phosphateisomerase, horseradish peroxidase, alkaline phosphatase, asparaginase,glucose oxidase, beta-galactosidase, ribonuclease, urease, catalase,glucose-6-phosphate dehydrogenase, glucoamylase andacetylcholinesterase. The detection can be accomplished by colorimetricmethods that employ a chromogenic substrate for the enzyme. Detectionmay also be accomplished by visual comparison of the extent of enzymaticreaction of a substrate in comparison with similarly prepared standards.

Detection may also be accomplished using any of a variety of otherimmunoassays. For example, by radioactively labeling the antibodies orantibody fragments, it is possible to detect fingerprint gene wild-type,mutant, or expanded peptides through the use of a radioimmunoassay (RIA)(see, e.g., Weintraub, B., Principles of Radioimmunoassays, SeventhTraining Course on Radioligand Assay Techniques, The Endocrine Society,March, 1986). The radioactive isotope can be detected by such means asthe use of a gamma counter or a scintillation counter or byautoradiography.

It is also possible to label the antibody with a fluorescent compound.When the fluorescently labeled antibody is exposed to light of theproper wave length, its presence can then be detected due tofluorescence. Among the most commonly used fluorescent labelingcompounds are fluorescein isothiocyanate, rhodamine, phycoerythrin,phycocyanin, allophycocyanin, o-phthaldehyde and fluorescamine.

The antibody can also be detectably labeled using fluorescence emittingmetals such as ¹⁵²Eu, or others of the lanthanide series. These metalscan be attached to the antibody using such metal chelating groups asdiethylenetriaminepentacetic acid (DTPA) or ethylenediamine-tetraaceticacid (EDTA).

The antibody also can be detectably labeled by coupling it to achemiluminescent compound. The presence of the chemiluminescent-taggedantibody is then determined by detecting the presence of luminescencethat arises during the course of a chemical reaction. Examples ofparticularly useful chemiluminescent labeling compounds are luminol,isoluminol, theromatic acridinium ester, imidazole, acridinium salt andoxalate ester.

Likewise, a bioluminescent compound may be used to label the antibody ofthe present invention. Bioluminescence is a type of chemiluminescencefound in biological systems in which a catalytic protein increases theefficiency of the chemiluminescent reaction. The presence of abioluminescent protein is determined by detecting the presence ofluminescence. Important bioluminescent compounds for purposes oflabeling are luciferin, luciferase and aequorin.

Throughout this application, various publications, patents and publishedpatent applications are referred to by an identifying citation. Thedisclosures of these publications, patents and published patentspecifications referenced in this application are hereby incorporated byreference into the present disclosure to more fully describe the stateof the art to which this invention pertains.

The following examples are intended only to illustrate the presentinvention and should in no way be construed as limiting the subjectinvention.

EXAMPLES Example 1: Generation of Mice Comprising CYT28 Gene Disruptions

To investigate the role of serpentine receptors, disruptions in CYT28genes were produced by homologous recombination. Specifically,transgenic mice comprising disruptions in CYT28 genes were created. Moreparticularly, as shown in FIG. 4, a CYT28-specific targeting constructhaving the ability to disrupt a CYT28 gene, specifically comprising SEQID NO:1, was created using as the targeting arms (homologous sequences)in the construct the oligonucleotide sequences identified herein as SEQID NO:3 or SEQ ID NO:4.

The targeting construct was introduced into ES cells derived from the129/OlaHsd mouse substrain to generate chimeric mice. The F1 mice weregenerated by breeding with C57BL/6 females, and the F2 homozygous mutantmice were produced by intercrossing F1 heterozygous males and females.

The transgenic mice comprising disruptions in CYT28 genes were analyzedfor phenotypic changes and expression patterns, as set forth below.

Example 2: Expression Analysis by RT-PCR

Total RNA was isolated from the organs or tissues from adult C57BL/6wild-type mice. RNA was DNaseI treated, and reverse transcribed usingrandom primers. The resulting cDNA was checked for the absence ofgenomic contamination using primers specific to non-transcribed genomicmouse DNA. cDNAs were balanced for concentration using HPRT primers.

RNA transcripts were detectable in all tissues analyzed: brain, cortex,subcortical region, cerebellum, brainstem, olfactory bulb, spinal cord,eye, Harderian gland, heart, lung, liver, pancreas, kidneys, spleen,thymus, lymph nodes, bone marrow, skin, gallbladder, urinary bladder,pituitary gland, adrenal gland, salivary gland, skeletal muscle, tongue,stomach, small intestine, large intestine, cecum, testis, epididymis,seminal vesicle, coagulating gland, prostate gland, ovary, uterus andwhite fat.

Example 3: Expression Analysis by LacZ Reporter Gene Analysis

Procedure: In general, tissues from 7-12 week old heterozygous mutantmice were analyzed for lacZ expression. Organs from heterozygous mutantmice were frozen, sectioned (10 μm), stained and analyzed for lacZexpression using X-Gal as a substrate for beta-galactosidase, followedby a Nuclear Fast Red counterstaining.

In addition, for brain, wholemount staining was performed. The dissectedbrain was cut longitudinally, fixed and stained using X-Gal as thesubstrate for beta-galactosidase. The reaction was stopped by washingthe brain in PBS and then fixed in PBS-buffered formaldehyde.

Wild-type control tissues were also stained for lacZ expression toreveal any background or signals due to endogenous beta-galactosidaseactivity. The following tissues can show staining in the wild-typecontrol sections and are therefore not suitable for X-gal staining:small and large intestines, stomach, vas deferens and epididymis. It hasbeen previously reported that these organs contain high levels ofendogenous beta-galactosidase activity.

LacZ (beta-galactosidase) expression was detectable in all tissuesanalyzed: brain, spinal cord, sciatic nerve, eyes, Harderian glands,thymus, spleen, lymph nodes, bone marrow, aorta, heart, lung, liver,gallbladder, pancreas, kidney, urinary bladder, trachea, larynx,esophagus, thyroid gland, pituitary gland, adrenal glands, salivaryglands, tongue, skeletal muscle, skin, male and female reproductivesystems. Most striking expression was observed in neuronal tissues andkidney.

Brain: In wholemount staining very strong lacZ expression was detectablethroughout the whole brain. On coronal sections very strong lacZexpression was detectable throughout the cerebrum. In cerebellum strongX-Gal signals were present in granular layer and white matter. FaintlacZ expression was detectable in the molecular layer.

Spinal cord: Strong lacZ expression was detectable throughout thecomplete spinal cord.

Sciatic Nerve: LacZ expression was detectable in nerves and in theperineurium.

Eyes: Weak lacZ expression was detectable in the inner nuclear andganglion cell layer of the retina. Strong expression was detectable inextraocular muscle and adipose tissue.

Harderian Glands: Strong lacZ expression was detectable in distinctcells.

Thymus: LacZ expression was detectable in cortex and medulla.

Spleen: LacZ expression is detectable in white pulp and blood vessels.

Lymph Nodes: LacZ expression was detectable in distinct cells and inperinodal adipose tissue.

Bone Marrow Smear: LacZ expression was detectable in megakaryocytes andother cells.

Aorta: LacZ expression was detectable in the periaortic adipose tissue.

Heart: LacZ expression was detectable in myocardium and atrium.

Lung: LacZ expression was detectable in bronchioli, alveoli andpulmonary vessels.

Liver: Weak lacZ expression was detectable in bile ducts and bloodvessels.

Gallbladder: A few cells expressed lacZ weakly.

Pancreas: LacZ expression was detectable in islets of Langerhans, ducts,blood vessels and connective tissue. Few acinar cells displayed X-Galstaining.

Kidney: Very strong lacZ expression was detectable in tubules, all cellsof medulla and papilla. Weaker expression was detectable in pelvis,glomeruli and blood vessels.

Urinary Bladder: LacZ expression was detectable in muscularis, mucosaand blood vessels.

Trachea: LacZ expression was detectable in mucosal epithelium,submucosa, blood vessels, peritracheal adipose tissue and nerves.

Larynx: Strong lacZ expression was detectable in the laryngealepithelium and submucosal glands.

Esophagus: LacZ expression was detectable in the squamous epitheliumlining, lamina propria and muscle layer.

Thyroid Gland: Many cells expressed lacZ moderately to strongly.

Pituitary Gland: LacZ expression was detectable in pars distalis, parsintermedia and pars nervosa.

Adrenal Glands: Strong lacZ expression was detectable in a few cells inthe capsule and in surrounding adipose tissue. Weaker X-Gal signals weredetectable in cortex and medulla.

Salivary Glands: Strong lacZ expression was detectable in sublingual andsubmandibular glands, especially in ducts.

Tongue: Strong lacZ expression was detectable in muscle fibers, minorsalivary and mucous glands. Further lacZ expression was detectable innerves, blood vessels, lamina propria and epithelium.

Skeletal Muscle: LacZ expression was detectable is throughout the musclein fibroblast-like cells and in blood vessels.

Skin: LacZ expression was detectable in epidermis, dermis and hairfollicles.

Skin of the Ear: LacZ expression was detectable in epidermis, dermis,muscle, cartilage, hair follicles and sebaceous glands.

Male Reproductive Systems: In the testis, strong lacZ expression wasdetectable in seminiferous tubules. Very faint X-Gal signals wereobserved in blood vessels. In the penis, lacZ expression was detectablein skin and blood vessels. In the seminal vesicles, lacZ expression wasdetectable in mucosa. In the coagulating gland, lacZ expression wasdetectable in mucosa. In the prostate and ampullary gland, lacZexpression was detectable in mucosa. Strong lacZ expression wasdetectable in ganglia.

Female Reproductive Systems: In the ovary. lacZ expression wasdetectable in follicles and interstitium. In the oviduct/uterus, lacZexpression was detectable in Fallopian tubules, myometrium, endometriumand blood vessels. In the vagina/cervix, lacZ expression was detectablein stroma, blood vessels and ganglia. Strongest signals are observed inganglia.

Example 4: Physical Examination

A complete physical examination was performed on each mouse. Mice werefirst observed in their home cages for a number of generalcharacteristics including activity level, behavior toward siblings,posture, grooming, breathing pattern and sounds, and movement. Generalbody condition and size were noted as well identifying characteristicsincluding coat color, belly color, and eye color. Following a visualinspection of the mouse in the cage, the mouse was handled for adetailed, stepwise examination. The head was examined first, includingeyes, ears, and nose, noting any discharge, malformations, or otherabnormalities. Lymph nodes and glands of the head and neck werepalpated. Skin, hair coat, axial and appendicular skeleton, and abdomenwere also examined. The limbs and torso were examined visually andpalpated for masses, malformations or other abnormalities. Theanogenital region was examined for discharges, staining of hair, orother changes. If the mouse defecates during the examination, the feceswere assessed for color and consistency. Abnormal behavior, movement, orphysical changes may indicate abnormalities in general health, growth,metabolism, motor reflexes, sensory systems, or development of thecentral nervous system.

Example 5: Necropsy Analysis

Necropsy was performed on mice following deep general anesthesia,cardiac puncture for terminal blood collection, and euthanasia. Bodylengths and body weights were recorded for each mouse. The necropsyincluded detailed examination of the whole mouse, the skinned carcass,skeleton, and all major organ systems. Lesions in organs and tissueswere noted during the examination. Designated organs, from whichextraneous fat and connective tissue have been removed, were weighed ona balance, and the weights were recorded. Weights were obtained for thefollowing organs: heart, liver, spleen, thymus, kidneys, andtestes/epididymides.

Certain lesions were present in homozygous mutant mice when compared towild-type control mice. In particular, certain of the homozygous miceexhibited a mesenteric mass that correlated with a lipoma observed athistopathalogical examination.

Example 6: Histopathological Analysis

Harvested organs were fixed in about 10% neutral buffered formalin for aminimum of about 48 hours at room temperature. Tissues were trimmed andsamples taken to include the major features of each organ. If anyabnormalities were noted at necropsy or at the time of tissue trimming,additional sample(s), if necessary, were taken to include theabnormalities so that it is available for microscopic analysis. Tissueswere placed together, according to predetermined groupings, in tissueprocessing cassettes. All bones (and any calcified tissues) weredecalcified with a formic acid or EDTA-based solution prior to trimming.

The infiltration of the tissues by paraffin was performed using anautomated tissue processor. Steps in the cycle included dehydrationthrough a graded series of ethanols, clearing using xylene or xylenesubstitute and infiltration with paraffin. Tissues were embedded inparaffin blocks with a standard orientation of specified tissues withineach block. Sections were cut from each block at a thickness of about3-5 μm and mounted onto glass slides. After drying, the slides werestained with hematoxylin and eosin (H&E) and a glass coverslip wasmounted over the sections for examination.

When compared to wild-type control mice, homozygous mutant miceexhibited a brain abnormality. In particular, homozygous mutant miceexhibited cortical malformation, particularly in the cerebellum. Morespecifically, the cortical malformation was observed in homozygousmutant mice at about 49 days of age and at about 300 days of age.Specifically, the homozygous mutant mice exhibited dysplasia of thelayers in the cerebellar cortex. In these homozygous mice, the granularcell and Purkinje cell layers were irregularly formed.

Certain homozygous mice additionally or alternatively exhibited a lipomathat correlated with a mesenteric mass seen at necropsy (see Example 5above). Certain other homozygous mice additionally or alternativelyexhibited a Leydig cell adenoma of the testis.

Example 7: Hematological Analysis

Blood samples were collected via a terminal cardiac puncture in asyringe. About one hundred microliters of each whole blood sample weretransferred into tubes pre-filled with EDTA. Approximately 25microliters of the blood was placed onto a glass slide to prepare aperipheral blood smear. The blood smears were later stained withWright's Stain that differentially stained white blood cell nuclei,granules and cytoplasm, and allowed the identification of different celltypes. The slides were analyzed microscopically by counting and notingeach cell type in a total of 100 white blood cells. The percentage ofeach of the cell types counted was then calculated. Red blood cellmorphology was also evaluated.

Microscopic examinations of blood smears were performed to provideaccurate differential blood leukocyte counts. The leukocyte differentialcounts were provided as the percentage composition of each cell type inthe blood.

Example 8: Serum Chemistry

Blood samples were collected via a terminal cardiac puncture in asyringe. One hundred microliters of each whole blood sample wastransferred into a tube pre-filled with EDTA. The remainder of the bloodsample was converted to serum by centrifugation in a serum tube with agel separator. Each serum sample was then analyzed as described below.Non-terminal blood samples for aged mice are collected via retro-orbitalvenous puncture in capillary tubes. This procedure yields approximately200 uL of whole blood that is either transferred into a serum tube witha gel separator for serum chemistry analysis (see below), or into a tubepre-filled with EDTA for hematology analysis.

The serum was analyzed for the following parameters: alanineaminotransferase, albumin, alkaline phosphatase, aspartate transferase,bicarbonate, total bilirubin, blood urea nitrogen, calcium, chloride,cholesterol, creatine kinase, creatinine, globulin, glucose, highdensity lipoproteins (HDL), lactate dehydrogenase, low densitylipoproteins (LDL), osmolality, phosphorus, potassium, total protein,sodium, and triglycerides.

Example 9: Densitometric Analysis

Mice were euthanized and analyzed using a PIXImus™ densitometer. Anx-ray source exposed the mice to a beam of both high and low energyx-rays. The ratio of attenuation of the high and low energies allowedthe separation of bone from soft tissue, and, from within the tissuesamples, lean and fat. Densitometric data including Bone Mineral Density(BMD presented as g/cm2), Bone Mineral Content (BMC in g), bone andtissue area, total tissue mass, and fat as a percent of body soft tissue(presented as fat %) were obtained and recorded.

Example 10: Embryonic Development

Animals are genotyped using one of two methods. The first method usesthe polymerase chain reaction (PCR) with target-specific and Neo primersto amplify DNA from the targeted gene. The second method uses PCR andNeo primers to “count” the number of Neo genes present per genome.

If homozygous mutant mice are not identified at weaning (3-4 weeks old),animals were assessed for lethality linked with the introduced mutation.This evaluation included embryonic, perinatal or juvenile death.

Newborn mice were genotyped 24-48 hours after birth and monitoredclosely for any signs of stress. Dead/dying pups were recorded andgrossly inspected and if possible, genotyped. In the case of perinataldeath, late gestation embryos (˜E19.5, i.e., 19.5 days post-coitum) ornewborn pups were analyzed, genotyped and subject to furthercharacterization.

If there was no evidence of perinatal or juvenile lethality,heterozygous mutant mice were set up for timed pregnancies. Routinely,E10.5 embryos are analyzed for gross abnormalities and genotyped.Depending on these findings, earlier (routinely >E8.5) or laterembryonic stages are characterized to identify the approximate time ofdeath. If no homozygous mutant progeny are detected, blastocysts (E3.5)are isolated, genotyped directly or grown for 6 days in culture and thengenotyped. Any suspected genotype-related gross abnormalities arerecorded.

Example 11: Fertility

The reproductive traits of male and female homozygous mutant mice aretested to identify potential defects in spermatogenesis, oogenesis,maternal ability to support pre- or post-embryonic development, ormammary gland defects and ability of the female knockout mice to nursetheir pups.

Homozygous mutant (−/−) mice of each gender were set up in a fertilitymating with either a wild-type (+/+) mate or a homozygous mutant mouseof the opposite gender at about seven to about ten weeks of age. Thenumbers of pups born from one to three litters were recorded at birth.Three weeks later, the live pups were counted and weaned.

Males and females were separated after they had produced two litters orat six months (26 weeks) of age, whichever comes first.

Example 12: Behavioral Analysis—Open Field Test

The Open Field Test was used to examine overall locomotion and anxietylevels in mice. Increases or decreases in total distance traveled overthe test time are an indication of hyperactivity or hypoactivity,respectively.

The open field provides a novel environment that creates anapproach-avoidance conflict situation in which the animal desires toexplore, yet instinctively seeks to protect itself. The chamber islighted in the center and has no places to hide other than the corners.A normal mouse typically spends more time in the corners and around theperiphery than it does in the center. Normal mice however, will ventureinto the central regions as they explore the chamber. Anxious mice spendmost of their time in the corners, with almost no exploration of thecenter, whereas bold mice travel more, and show less preference for theperiphery versus the central regions of the chamber.

Each mouse was placed gently in the center of its assigned chamber.Tests were conducted for 10 minutes, with the experimenter out of theanimals' sight. Immediately following the test session, the fecal boliwere counted for each subject: increased boli are also an indication ofanxiety. Activity of individual mice was recorded for the 10-minute testsession and monitored by photobeam breaks in the x-, y- and z-axes.Measurements taken included total distance traveled, percent of sessiontime spent in the central region of the test apparatus, and averagevelocity during the ambulatory episodes. Increases or decreases in totaldistance traveled over the test time indicate hyperactivity orhypoactivity, respectively. Alterations in the regional distribution ofmovement indicates anxiety phenotypes, i.e., increased anxiety if thereis a decrease in the time spent in the central region.

When compared to age- and gender-matched wild-type control mice (+/+),homozygous (−/−) mutant mice had displayed a higher average velocitythan wild-types in the open field test, indicating that mutantsexhibited decreased anxiety and/or increased mobility and/or increasedactivity (e.g., hyperactivity).

Example 13: Behavioral Analysis—Rotarod Test

The Accelerating Rotarod was used to screen for motor coordination,balance and ataxia phenotypes. Mice were allowed to move about on theirwire-cage top for 30 seconds prior to testing to ensure awareness. Micewere placed on the stationary rod, facing away from the experimenter.The “speed profile” programs the rotarod to reach 60 rpm after sixminutes. A photobeam was broken when the animal fell, which stopped thetest clock for that chamber. The animals were tested over three trialswith a 20-minute rest period between trials, after which the mice werereturned to fresh cages. The data was analyzed to determine the averagespeed of the rotating rod at the fall time over the three trials. Adecrease in the speed of the rotating rod at the time of fall comparedto wild-types indicated decreased motor coordination possibly due to amotor neuron or inner ear disorder.

Example 14: Behavioral Analysis—Startle Test

The startle test screens for changes in the basic fundamental nervoussystem or muscle-related functions. The startle reflex is ashort-latency response of the skeletal musculature elicited by a suddenauditory stimulus. This includes changes in 1) hearing—auditoryprocessing; 2) sensory and motor processing—related to the auditorycircuit and culminating in a motor related output; 3) global sensorychanges; and motor abnormalities, including skeletal muscle or motorneuron related changes.

The startle test also screens for higher level cognitive functions. Thestartle reflex can be modulated by negative affective states like fearor stress. The cognitive changes include: 1) sensorimotor processingsuch as sensorimotor gating changes related to schizophrenia; 2)attention disorders; 3) anxiety disorders; and 4) thought disturbancedisorders.

The mice were tested in a San Diego Instruments SR-LAB sound responsechamber. Each mouse was exposed to 9 stimulus types that were repeatedin pseudo-random order ten times during the course of the entire25-minute test. The stimulus types in decibels were: p80, p90, p100,p110, p120, pp80, p120, pp90, p120, pp100, and p120; where p=40 msecpulse, pp=20 msec prepulse. The length of time between a prepulse and apulse was 100 msec (onset to onset). The mean Vmax of the tenrepetitions for each trial type was computed for each mouse.

Example 15: Behavioral Analysis—Hot Plate Test

The hot plate analgesia test was designed to indicate an animal'ssensitivity to a painful stimulus. The mice were placed on a hot plateof about 55.5° C., one at a time, and latency of the mice to pick up andlick or fan a hindpaw was recorded. A built-in timer was started as soonas the subjects were placed on the hot plate surface. The timer wasstopped the instant the animal lifted its paw from the plate, reactingto the discomfort. Animal reaction time was a measurement of theanimal's resistance to pain. The time points to hindpaw licking orfanning, up to a maximum of about 60-seconds, was recorded. Once thebehavior was observed, the animal was immediately removed from the hotplate to prevent discomfort or injury.

Homozygous mutant mice exhibited an increase in pain response or painsensitivity in the hot plate test. In particular, homozygous mutant micedisplayed shorter response latencies to lick their hindpaw in responseto a thermal stimulus, relative to wild-type control mice (See FIG. 5).This may suggest a role for CTY28 in pain or pain sensitivity, and mayreveal CTY28 as a target for the identification of new treatments andtherapeutic agents for pain. Such treatments and agents include theCTY28 gene, gene product, or other gene therapy methods, as well asagents that modulate CTY28.

Example 16: Behavioral Analysis—Tail Flick Test

The tail-flick test is a test of acute nociception in which ahigh-intensity thermal stimulus is directed to the tail of the mouse.The time from onset of stimulation to a rapid flick/withdrawal from theheat source is recorded. This test produces a simple nociceptive reflexresponse that is an involuntary spinally mediated flexion reflex.

Example 17: Behavioral Analysis—Metrazol Test

To screen for phenotypes involving changes in seizure susceptibility,the Metrazol Test was be used. About 5 mg/ml of Metrazol was infusedthrough the tail vein of the mouse at a constant rate of about 0.375ml/min. The infusion caused all mice to experience seizures. Those miceentering the seizure stage the quickest were thought to be more prone toseizures in general.

The Metrazol test can also be used to screen for phenotypes related toepilepsy. Seven to ten adult wild-type and homozygote males were used. Afresh solution of about 5 mg/ml pentylenetetrazole in approximately 0.9%NaCl was prepared prior to testing. Mice were weighed and loosely heldin a restrainer. After exposure to a heat lamp to dilate the tail vein,mice were continuously infused with the pentylenetetrazole solutionusing a syringe pump set at a constant flow rate. The following stageswere recorded: first twitch (sometimes accompanied by a squeak),beginning of the tonic/clonic seizure, tonic extension and survivaltime. The dose required for each phase was determined and the latency toeach phase was determined between genotypes. Alterations in any stagemay indicate an overall imbalance in excitatory or inhibitoryneurotransmitter levels.

Example 18: Behavioral Analysis—Tail Suspension Test

The tail suspension test is a single-trial test that measures a mouse'spropensity towards depression. This method for testing antidepressantsin mice was reported by Steru et al., (1985, Psychopharmacology85(3):367-370) and is widely used as a test for a range of compoundsincluding SSRI's, benzodiazepines, typical and atypical antipsychotics.It is believed that a depressive state can be elicited in laboratoryanimals by continuously subjecting them to aversive situations overwhich they have no control. It is reported that a condition of “learnedhelplessness” is eventually reached.

Mice were suspended on a metal hanger by the tail in an acoustically andvisually isolated setting. Total immobility time during the six-minutetest period was determined using a computer algorithm based uponmeasuring the force exerted by the mouse on the metal hanger. Anincrease in immobility time for mutant mice compared to wild-type micemay indicate increased “depression.” Animals that ceased strugglingsooner may be more prone to depression. Studies have shown that theadministration of antidepressants prior to testing increases the amountof time that animals struggle

As is apparent to one of skill in the art, various modifications of theabove embodiments can be made without departing from the spirit andscope of this invention. These modifications and variations are withinthe scope of this invention.

1. A transgenic mouse comprising a disruption in a CYT28 gene.